The FEV is one of the most repairable tanks you can buy. It is also one of the easiest to order the wrong part for.

The reason is simple: there are at least four separate factories making V4.5S+ variants - SXK, YFTK, ULTON and Rekavape - plus the original, and their parts are mostly interchangeable. Mostly is the dangerous word.

So instead of guessing, here is every compatibility statement we could verify from the product pages themselves, including the places where the page explicitly warns you off.

Glass: the easiest part to get right

Glass is where the FEV platform is most forgiving, because two manufacturers state cross-brand fit openly.

Part  |  Dimensions  |  Fits  |  Price

ULTON Replacement Glass Tube  |  Outer 20mm / inner 18mm / height 7mm / 10g  |  SXK + YFTK + ULTON V4.5S+  |  $2.49

SXK Replacement Glass Tube  |  10g  |  SXK + YFTK V4.5S+  |  $2.59

Rekavape E-Vapor Glass  |  22mm / 3.5ml  |  Rekavape E-Vapor V4.5S+  |  $2.99

Top Tank Glass 4ml  |  23mm / 4ml  |  FEV V4.5S+ / V4.5 4ml top tube (SKU27077)  |  $2.39

Top Tank Glass 2ml  |  23mm / 2ml  |  FEV V4.5S+ / V4.5 2ml top tube (SKU27076)  |  $2.39

Note the difference between the first two rows. The ULTON tube is listed for three brands; the SXK tube is listed for two. Both are $2.50-ish. If you are buying glass just in case, take the ULTON one - the same money covers one more brand.

The 4ml and 2ml glass in the last two rows are a different part entirely. They are the glass for the top tank tube, not the main tank body, so they are not interchangeable with the first three rows even though they all say "FEV glass." Read the fitment line on each page, not the product title.

Complete tank assemblies, if you would rather replace the whole top

Sometimes it is easier to replace the entire upper section than to hunt for one piece of glass. Two options, both 23mm:

Assembly  |  Capacity  |  Material  |  Price

Steam Tuners Nano Tank + Chimney  |  2.5ml  |  PC + SS chimney, 23mm, 12g  |  $7.99

Steam Tuners Tank + Chimney  |  3.5ml  |  PC + SS chimney, 23 x 30mm, 12g  |  $6.99

YFTK Tank Tube Kit  |  3.5ml  |  23mm  |  $11.59

PEI Top Tank Tube  |  3.5ml  |  PEI, 23mm  |  $9.99

These swap the tank capacity as well as the material. Putting a 2.5ml Nano tank on a V4.5S+ makes the whole atomizer shorter and more pocket-friendly; the 3.5ml versions sit between the stock 4.5ml and the Nano. If your reason for replacing is "the glass broke," buy glass. If your reason is "this thing is too tall," buy one of these instead.

Why PEI and PC exist at all

Glass is the clearest and most chemically inert option, but it breaks. PC and PEI are the practical alternatives - they will not shatter if the tank takes a knock, and PEI in particular handles heat well. The trade is that neither is as clear as glass, and PEI comes in that amber/yellow tone rather than clear.

If you vape citrus or cinnamon-heavy liquids, be aware that polycarbonate is not the material for you - those flavours are known to attack PC. Glass or PEI is the safer choice.

Decks: where compatibility gets narrower

The build deck is where "mostly interchangeable" starts to bite.

The Improved Build Deck Base ($8.90) is unusually generous for a deck. The product page lists it as fitting:

• SXK FEV V4.5S+
• ULTON FEV V4.5S+
• YFTK FEV V4.5S+
• ULTON FEV V4.5M
• ULTON FEV 4.5
• ULTON FEV V4

That is six variants across three factories. 22.5 x 22.5mm, 21mm tall, 37g. The "improved" refers to the wiring and wicking layout - the page states it is easier to wire and wick and produces denser cloud and more flavour than the older base.

If you have a V4.5S+ from any of those three makers and your deck threads or posts are worn, this is the replacement to buy. If you have something else, ask first.

The chamber reducer: read the warning

The ULTON PEEK Chamber Reducer V2 ($5.79) is the part that most improves the FEV's flavour, and the one with the most explicit compatibility warning on our site.

The product page says it is compatible with original Flash e-Vapor V4, V4.5S and V4.5S+, ULTON FEV V4.5S+ and YFTK FEV V4.5S+ - and then adds:

"We do not guarantee the compatibility of other fev atomizers due to tolerance, it only works for 1:1 fev."

That is not marketing hedging. FEV chamber dimensions have real manufacturing tolerance between factories, and a PEEK insert that must seat precisely will not tolerate much variation. If you do not know which factory made your FEV, email us before ordering this part.

Installing it is straightforward: remove the airflow control screw and assemble the reducer into the chamber. It does not change your airflow - it reduces chamber volume so the vapour is denser.

Bottom sections and airflow parts

Part  |  What it does  |  Fits  |  Price

Bottom Air Intake Base  |  Replaces the base section, 316SS, 23mm  |  V4 / V4.5 / V4.5S+  |  $13.99

ULTON Dual Airflow Part  |  Converts toward direct lung  |  V4.5S+ (23 x 23mm)  |  $7.99

YFTK AFC Kit V2  |  Intake cover + MTL/DL rings, SS, 15g  |  V4.5 - V4.5S+  |  $14.89

SXK 316SS Wicks-DLC (2pcs)  |  The feed tubes that stop flooding  |  SXK + YFTK V4.5S+  |  $2.99

ULTON FEV Wicks (6pcs)  |  DLC-coated feed tubes  |  FEV V4.5S+  |  $2.99

The bottom air intake base is the widest-fit part on this page - it works across V4, V4.5 and V4.5S+. The AFC Kit V2 covers V4.5 through V4.5S+. These two are the safest cross-version purchases in the entire FEV ecosystem.

The part that saves your evenings: wicking inserts

If you take one thing from this article, take this. The FEV does not feed liquid the way a normal RTA does. Two small metal inserts sit in the deck and deliver juice up to the cotton. Without them, the deck floods.

A forum administrator, answering a new owner whose FEV was flooding regardless of cotton amount, put it directly:

"Have you got these two? Without these you'll have all manner of floods."

Another owner in the same thread diagnosed a photo of a flooding build by noting the wick was not sitting directly over the coil clamp screws, and therefore was not in line with the two fluid feed tubes. Alignment, not cotton quantity.

If your FEV is flooding and you have been adding and removing cotton for an hour, stop. Check the inserts are present, and check the wick is directly over the screws.

Quick compatibility summary

Part type  |  Cross-brand safe?

Air pins  |  Yes - ULTON 4-pack explicitly fits YFTK / ULTON / SXK / original

Glass tube (main)  |  Usually - ULTON fits 3 brands, SXK fits 2

Build deck  |  Mostly - improved base fits 6 variants

Bottom air intake base  |  Yes - V4 through V4.5S+

Chamber reducer  |  No - 1:1 FEV only, tolerance warning

Top tank assemblies  |  Check capacity - 2.5ml and 3.5ml are different parts

FAQ

My FEV is from an unknown factory. What can I safely buy?
Air pins, the bottom air intake base and the improved build deck are the safest - all three are listed across multiple variants. Avoid the PEEK chamber reducer until you know what you have.

Is "FEV glass" one part or several?
Several. The main tank tube glass (20mm outer for ULTON, listed for three brands) is a different part from the top tank tube glass (23mm, 2ml or 4ml). Check the fitment line, not the title.

Can I change my FEV's capacity without buying a new tank?
Yes. Steam Tuners 2.5ml and 3.5ml tank-and-chimney assemblies, the YFTK 3.5ml tube kit, and the PEI 3.5ml top tube all change capacity on a V4.5S+.

Will PEI or PC break like glass?
No, that is the point. They resist impact. The trade is clarity and, for PC, sensitivity to citrus and cinnamon flavours.

Do these parts fit the FEV V6?
The V6 is a different, shorter 2ml design. Do not assume V4.5S+ parts fit it - check each product page.

Related reading

• Customer reviews
• All FEV products
• All replacement tanks and upgrade kits
• 510 drip tips
• Current offers
• Shipping and tracking

Not sure which version you have? Send us a photo of the deck and the base, and we will tell you which parts fit before you order.