The Digiflavor Siren V4 MTL RTA review marks virgin territory for me, although I’m well aware of their products I’ve never used one, so I have no idea as to what to expect.

Digiflavor is a Shenzen based manufacturer who were established back in 2016 by parent company Geekvape, with the moto of “It’s time to make the world better” it wasn’t long before their first Siren MTL tank hit the vape market.

Digiflavor Siren V4 RTA hand check pic 1

In 2017 the Digiflavor Siren 25 GTA, a dedicated single coil MTL RTA was released boasting a 5ml juice capacity. Reviewer John Summers was pretty smitten with it.

A year later, our Laura-ann Burgess took us through the ins and outs of the Siren 2 GTA. The reduced tank capacity was more than compensated for by an upgraded build deck. This meant more room for a larger coil – it was even possible to achieve a restrictive direct lung vape.

In 2020 the Siren 3 GTA made a guest appearance as part of the Digiflavor Z1 SBS kit. The side mounted screws were ditched in favour of top mounted. This improved the build process by making coil installation much simpler.

It’s been said that Geekvape created Digiflavor as a way of catering exclusively for the MTL vaper.

The Digiflavor Siren V4 MTL RTA certainly galvanises that ideology by going full circle. It repeats the same width, GTA style build deck and two post design of the five year old original.

What Can We Expect From the Digiflavor Siren V4 MTL RTA?

It looks like the build deck will accommodate anything up to a 3mm inner diameter coil.

So we shouldn’t necessarily expect to be running with ultra low wattage typically associated with MTL vaping, that’s the fun of experimenting with coil builds.

Digiflavor Siren V4 RTA boxed image

The tiny yet well balanced honeycomb airflow structure built into the deck will have an impact on cloud production.

It’s likely to be improved somewhat if using micro coils or diameters of around 2 – 2.5mm. So expect coil sizes to have an impact.

The height of the tank has been shrunk over previous versions. Expect step doming and close proximity of the coil to the drip tip to increase and concentrate the flavour.

Inside the Box

I’m sure this is a review edition so the external packaging is likely to differ should you decide to partake.

An outer sleeve features a simplistic Digiflavor logo with branding on either side.

Digiflavor Siren V4 RTA unboxed

Removing this reveals the inner packaging and a lid that’s easily pulled off. Inside we get:

  • Siren V4 MTL RTA
  • Clapton Ni80 1.2ohm coil
  • Fused Clapton Ni80 1.4ohm coil
  • Braided coil KA1 0.65ohm
  • Fused Clapton SS316L 1.0ohm coil
  • 4 x cotton aglet
  • Spare 510 drip tip
  • Accessory bag
  • Instruction manual

Digiflavor Siren V4 MTL RTA – Key Features

It features a raised GTA style build deck for efficient under coil wicking and improved flavour.

A top mounted post screw and clamp design make installing and trimming the coil much easier.

Digiflavor Siren V4 RTA logo on side of packaging

The semi hidden linear bottom airflow has been designed for even distribution of airflow while also preventing leakage. The AFC ring incorporates a red marker to denote the level of MTL airflow restriction.

Micro knurling has been etched into the tank in various places, allowing for easy removal of parts for maintenance and cleaning.

There’s a choice of four different colour schemes which are Black, Stainless steel, Rainbow and Gunmetal (under review).

Digiflavor Siren V4 MTL RTA – Specifications

I noticed some confusion as to the height of the RTA when checking with various sites.

There seemed to be some conflicting specs, most probably due to including the drip tip with their calculations.

  • Material Stainless steel
  • Weight 43g
  • Height 28.5mm (without drip tip)
  • Diameter 22mm
  • Tank material PEI
  • Tank capacity 2ml
  • Airflow Adjustable
  • Deck Single coil two post GTA design
  • Thread 510

Digiflavor Siren V4 MTL RTA – Design and Build Quality

It’s been suggested in the past that earlier versions of the RTA have also been able to offer a restrictive direct lung vape.

Nothing of the design and build quality of this latest offering would suggest anything other than a dedicated MTL vaping product.

To begin with there’s the radical difference in height. From the top cap to the underside of the deck the tank measures a mere 28.5mm.

That doesn’t make it much taller than my beloved OFRF Gear RTA – my all time favourite single coil MTL device.

Digiflavor Siren V4 MTL RTA Drip Tips

Pick from a choice of two, and thank vape heaven for that because the extended drip tip is a complete monstrosity.

At around 23mm in height it looks totally out of place and does much to tarnish the aesthetics of the tank.

Digiflavor Siren V4 RTA close up of extended 510 drip tip

The narrow bores of both measure around 3mm so heavy airflow restriction is the order of the day from these 510 drip tips.

Two O rings are included so they both sit snug inside the catch cup of the top cap. This does mean you can replace either with a choice of your own – I did!

510 Connector Pin

The gold plated 510 connector protrudes and is surrounded by a thin ring of peak insulation.

It will allow for coupling with a hybrid mod if that’s your bag.

Digiflavor Siren V4 RTA gold plated 510 pin

A MTL device on a hybrid mod? Nah – not for me..

On the base is the Digiflavor logo alongside the product serial number.

Digiflavor Siren V4 MTL RTA Top Cap and Fill Ports

It’s a very tidy arrangement with the top cap, facilitated by some fine micro knurling. The threading is butter smooth and very well engineered.

It only takes a few counter clockwise turns to release the top cap. There was a distinct absence of grinding, crunching or squeaking – great build quality.

Digiflavor Siren V4 RTA top cap unscrewed from tank section

The steel plating on the underside has a finish as smooth as glass although I did notice a degree of chatter around the fill ports themselves.

The Digiflavor Siren V4 MTL RTA incorporates two kidney shaped fill ports each measuring approximately 7mm wide. There shouldn’t be any issues with bottle nozzle sizes.

Digiflavor Siren V4 RTA kidney shaped fill ports

Digiflavor Siren V4 MTL RTA Airflow Design

This one had me flummoxed to begin with!

Although there’s airflow adjustability, I couldn’t quite fathom out how it worked.

Digiflavor Siren V4 RTA red airflow adjustment indicator

It wasn’t until I removed the AFC ring that it made any sense.

There are a series of “hidden” airflow slots that sit behind the control ring. They’re all the same size and representative of the Digiflavor Linear airflow structure.

Digiflavor Siren V4 RTA hidden airflow structure

The AFC ring has a notch carved into its side so when positioned will open or close the airflow slots. The external red marker indicates the degree of restriction.

Digiflavor Siren V4 RTA airflow control ring removed showing airflow notch

The Tank

It’s 2ml in line with current TPD regulations and made from PEI which is similar to PEEK material but less resistant to higher temperatures.

As a thermoplastic it’s usually transparent or amber in colour with a high degree of rigidity.

Digiflavor Siren V4 RTA PEI tank close up image

I’ve two issues with this tank. First it lacks much of a viewing window and secondly it’s difficult to gauge just how much of the tank has been filled.

I’m forced to squint down the fill port to check the levels. I couldn’t find any way of removing the PEI for cleaning either. So maybe that should read three issues lol.

Inside the Tank

It’s more a case of stepped doming on the inner chimney and maybe a little less than I was expecting.

The machine quality here though is top notch and looks very high end.

Digiflavor Siren V4 RTA inner doming of the chimney section

There are three juice flow ports incorporated around the inner threading allowing juice to drop beneath the raised deck. The cotton wicks are perpetually gravity fed.

Digiflavor Siren V4 RTA inside the chimney

GTA Style Build Deck

Now we move onto the star of the show, the build deck.

It retains the same GTA style as its predecessors, and by being raised it allows the wicks to be fed from a 5mm deep juice well surrounding it.

Digiflavor Siren V4 RTA build deck pic 1

The two slotted post screws are gold plated but look soft and fragile. Only time will tell if they are easily stripped. They also look a little out of place but since they’re hidden it’s no real biggie.

In the centre of the deck sits a circular honeycomb airflow intake, the strength of which is influenced via the Linear AFC ring.

Digiflavor Siren V4 RTA top down view of GTA style build deck

On either side of this are the juice wicking ports, constantly supplied by that deep juice well.

Digiflavor Siren V4 RTA – How To Build and Wick


I’m not the best and certainly not the most patient given that my eyesight is rapidly failing me! lol

First things first. Remove the deck from the tank by unscrewing clockwise.

Digiflavor Siren V4 RTA unscrewing the post screws

Loosen both post screws so that the coil legs are able to pass through the clamps.

Position the coil legs through the clamps and carefully tighten the post screws.

The coil needs to be sitting directly above the air intake and at a height of around 2mm off the deck.

RTA coil positioning inside post clamps

Trim away the excess of coil leg as close to the sides of the build deck as possible. This will avoid any possible shorting through contact with the inner chimney.

RTA trimming the coil legs flush

Preferably using a dedicated build tab slowly dry pulse the coil. Ensure all hot spots are removed. If they persist try strumming the coil surface with an appropriate tool.

The coil needs to heat up evenly from the centre outwards.

Digiflavor Siren V4 RTA test firing the coilOnce the coil has cooled down pass a cotton aglet through its centre. Make sure it fits snug but not so tight as to deform the coil.

Digiflavor Siren V4 RTA pulling the cotton through the coilTrim the cotton aglet to a length that allows it to sit within the juice wicking ports. You won’t need much and you shouldn’t need to thin/rake it.

 trimming the cotton to suitable sizeSaturate the cotton and the coil with E juice.

priming the cotton before placing into positionGently tuck the ends of the saturated cotton into the wicking ports making sure not to pack too tightly. There needs to be space for E liquid to circulate in and around the cotton.

RTA positioning the cotton after primingIt’s time to test fire the coil again. We’re checking for any last minute problems with shorting, wicking or vapour production.

 RTA priming and test firing the cotton and coilOnce you’re happy with everything, screw the tank back onto build deck.

RTA screwing the tank back onto the deckRemove the top cap by unscrewing counter clockwise. Gently pour E liquid into the fill port and replace the top cap.

You’re ready to vape!

Digiflavor Siren V4 MTL RTA – How Does It Perform?

Before we move onto flavour and cloud replication I feel I must mention the included coils.

They’re very soft and malleable which makes them prone to damage.

RTA MTL fused Clapton and Clapton included coils

Because of this I had a nightmare trying to install them. It wasn’t helped by the post clamp system as there was no way of holding them in place. On multiple occasions the coil legs simply pulled free.

When I finally did manage to secure them the level of distortion had rendered them useless. Any attempts at straightening them proved fruitless.

For this reason I opted to use my own MTL coil which was more robust.

Don’t get me wrong. It’s rare for a manufacturer to be so generous with coils but they just didn’t work for this impatient bugger!

Digiflavor Siren V4 Flavour and Cloud Production

The coil used was a Wotofo fused Clapton with an inner diameter of 2.5mm. It’s the smallest coil I could find but was a good fit for the build deck.

I used Riot Squad Sweet Strawberry which contained a hybrid nicotine content. I coupled it with the Voopoo Drag X Plus Pro running at 20W.

With airflow wide open I did notice a minor degree of turbulence but no spit back so that was a positive start, any attempts at a restrictive lung hit fell on very un-vape like ground.

– That’s to say it caused a few nasty coughing fits.

On this setting the flavour was already sparkling with lots of clarity, strawberry notes were clean and tasty.

I couldn’t even suggest this to be an airy MTL, it was just a very good starting point.

Other Airflow Adjustments

I dialed the airflow down to around mid restriction.

The tank began making more crackling sounds but again the flavour held up fantastically well.

This setting pretty much provided the perfect MTL vape.

I was able to recycle more of the vapour instead of it escaping out into the surrounding air. It was both was light and wispy, something any reformed smoker will appreciate.

So there was a accurate representation of the draw from a cigarette. It had a slight throat kick on this wattage setting but vapour production still remained discreet.

When closing the airflow further the vape was a little too tight but not enough to put the vape hardened MTL vaper off.

I felt the flavour starting to become more suppressed although still very good with the cooling agent tickling the taste buds.

It would also become a bit on the harsh side. I did notice mild throat irritation despite the hybrid nicotine content. The smoothness of an open airflow draw had certainly been lost.

I would recommend using juice ratios of 50VG/50PG in general with the Digiflavor Siren V4 MTL RTA, it’s perfectly suited for the size of coils the build deck caters for.

Just for interest value I tried a 70VG/30PG juice and it didn’t take long for a nasty dry hit to singe the back of the throat. I never learn!

Digiflavor Siren V4 Airflow Observations

The Digiflavor Siren V4 MTL RTA delivers all the airflow options you could ask for.

They range from a slightly airy draw that refuses to cross over into restrictive lung territory to the classic MTL vape well known to any recently converted smoker.

One of the most impressive observations was the accuracy of adjustment when using the Linear style AFC ring. It’s been honed to perfection making it possible to notice airflow differences even with the slightest of tweaks.

None of the airflow options seemed to have too much of an impact on flavour quality either.

Admittedly there was some dilution at higher restriction but by then the vape was too tight to be of use anyway.


  • Compact design
  • Great build quality – knurling, threading and machining
  • Excellent flavour and cloud production
  • Adjustable linear airflow works an absolute treat
  • No leaking


  • Difficulty in securing coil under post screws
  • Having to remove the tank from the mod to make airflow adjustments
  • The extended drip tip (subjective)
  • The lack of a viewing window

Final Review Verdict

As previously mentioned I had my fair share of woes installing a coil on the build deck. What normally takes five minutes ended up taking over half an hour.

All because the post screws were failing to clamp the coil down. To add insult to injury the soft gold plated flat head screws were already showing signs of wear and tear.

I think grub screws with standard post holes would have worked much better.

Airflow adjustment was impossible without removing the tank from the mod. I found this a massive annoyance because I’m one for tinkering, and it really shouldn’t be a thing these days.

For a tank that’s design so well I have no idea what Digiflavor were thinking about with the extended drip tip, it’s almost farcical. Either that or I’m just being the usual stick in the mud.

Digiflavor Siren V4 MTL RTA – Overall Performance

What it ultimately comes down to is performance and the Digiflavor Siren V4 RTA delivers by the vape load.

It provides one of the most satisfying MTL vapes I’ve experienced so far in 2021. This is due to the combination of airflow options, consistent flavour across those options and extremely well balanced vapour production.

The honeycomb intake ensures plenty of controlled airflow distribution under the coil which sits not far away from the drip tip itself. Combine this with some pin point tweaking of the airflow control ring and we’re onto a winner as far as flavour properties are concerned.

It’s not for the new vaper by any stretch.

It’s for someone that has knowledge of building, and for those tired of trying to source stock coils for their preferred MTL tank.

Above all it’s for anyone that craves consistency to their flavour across a multitude of mouth to lung airflow options.

So is it better than my beloved OFRF Gear RTA? Hmmmmm…

The excellent flavour qualities are matched to be honest, buthe Digiflavor Siren MTL RTA wins when it comes to build quality.

Digiflavor deliver delights with this one.

neil cozens
Neil Cozens

My name is Neil and I've been a keen vaper for eight years, having been smoke free since 2014. That's all thanks to being introduced to a CE4 clearomiser by a work mate. In 2015 I started a Facebook group encouraging members to help others make the switch, sharing thoughts and opinions while acknowledging all the hard work that goes into running a vape shop and the guidance those folks give. I've also created a You Tube channel, Ncboreas Vapes. It's primarily there to help the newer vaper so if you've any questions feel free to drop by! There are so many positives to vaping and absolutely none to smoking. It's a message I continue to spread. Long Live Vaping. Live Longer Vaping.

Build Quality
Ease of Use
Flavour and Cloud Production (based on the coil I used)
Replace if Lost
My name is Neil and I've been a keen vaper for eight years, having been smoke free since 2014. That's all thanks to being introduced to a CE4 clearomiser by a work mate. In 2015 I started a Facebook group encouraging members to help others make the switch, sharing thoughts and opinions while acknowledging all the hard work that goes into running a vape shop and the guidance those folks give. I've also created a You Tube channel, Ncboreas Vapes. It's primarily there to help the newer vaper so if you've any questions feel free to drop by! There are so many positives to vaping and absolutely none to smoking. It's a message I continue to spread. Long Live Vaping. Live Longer Vaping.
digiflavor-siren-v4-reviewDigiflavor isn't about to give up on a good thing and the Siren V4 MTL RTA performs to a level that's just about as good as it gets. The flavour quality is insanely good, boosted by a linear airflow structure that's hyper sensitive to adjustment. The deck can be tricky and will test the nerves of the most patient of builders. However, it's worth the effort for superb flavour and stealth like vapour production. Isn't that what every MTL vaper craves?


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