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Re-stock due in early 2022.



The hop units in this batch will all be GOLD, the nozzles in this batch will all be RED. Hop units and hop wheels will feature new CNC engraving, not lasered white. Hop wheels from normal stock will be BLACK unless purchased as part of an Underlever package.

We are aware of a compatibility problem between the V5 hop unit from this batch and the V3, V3.1 Tanuki HPA MP5 adaptor. The details of the problem and the relevant fix can be found here. The new adaptor part we developed with Tanuki can be found here. 


This is a 13-piece kit that provides you with all the parts required to make your KJW KC-02 compatible with the wide variety of VSR/GBB hop rubbers and VSR barrels out there in the airsoft world (because the standard KC-02 barrel, rubber and hop unit are proprietary to the KC-02), but also does soooo much more! Over a year of development and testing went into this kit, as well as an extensive beta-testing programme with airsoft tech experts around the world.

You can watch the walk-through and installation video here:

The diagram in the pictures explains much of the detail of each part, here's a high-res download link for it:

V5 Genesis kit now includes 2 cylinder cross-pins - plain and knurled. You can pick which pin you want to use when installing the cylinder. The knurled pin gives the best fit and seal but can be difficult to hammer in. The plain pin is much easier to install but will need to be SEALED IN PLACE WITH THIN LIQUID SUPERGLUE to stop it leaking gas and stop it dragging on the bolt carrier.

The kit contains 13 parts:

  • KC-VSR Cylinder-Nozzle V6, 7075 CNC aluminium, RED anodised
  • Genesis Hop Unit V5, 6061 CNC aluminium, GOLD anodised
  • Diadem Hop Wheel V3A, 7075 anodised CNC aluminium
  • 3 x Hop Keys: Arch, Bridge, Flat. 6061 anodised CNC aluminium
  • 3 x Flow Restrictors: Low (green), Medium (blue), High (red). 6061 anodised CNC aluminium. (Maximum power is achieved by not using a flow restrictor at all)
  • 2 x 3mm neodymium magnets, for use with standard KJW hop wheel
  • 1 x 2.5mm knurled steel cylinder cross-pin
  • 1 x 2.5mm plain steel cylinder cross-pin

This kit solves problems with poor air seal, solves the problem of broken cylinders, allows greater control of hop pressure and adjustment resolution, allows use of a huge range of existing VSR hop rubbers and barrels, and many other small improvements in functionality. It is a quantum leap forward in the performance and upgradeability of the KC-02 platform that has never been done successfully before.

Testing has shown that 60 degree hardness hop rubbers are best suited for this hop unit due to the amount of pressure it applies when using heavy ammo such as 0.36g - 0.4g weights.

70 degree hop rubbers are NOT advisable as they usually result in massive over-hopping and over-sensitivity of the adjustment wheel, even with 0.45g+ weight.

This kit does require some skill and special tools to install. The most difficult part is inserting the knurled pin into the cylinder without damaging the cylinder. We highly recommend watching the guide video ( to show you what we mean. We used a hammer and punch set to install ours, but our Beta testers reported it is easier to do very carefully with a vice to press the pin into position. WE WILL NOT BE REPLACING PARTS YOU DAMAGE DURING ASSEMBLY SO BE CAREFUL, WE DO NOT HAVE SPARES.

The latest improvements to the Genesis kit should reduce the amount of bedding-in time required after installing the new parts, but some manual dry-racking may still be required for a few minutes. We recommend plenty of lubrication then cleaning inside the gun once it cycles smoothly.

The most common area to cause problems is the top of your trigger mech above the valve striker where the cylinder slides across the top of the trigger mech. This area usually has some rough casting in the corners which needs to wear down to suit the new cylinder. This isn't a problem for everybody but some of our beta testers used a file to smooth this area first. We found that racking the gun a couple dozen times and cleaning, followed by just shooting the gun for a while was more than sufficient to cut this area to the new parts.

As always, contact us via Facebook if you've got any questions.

Barrel and Hop Rubber Combo's we've tested and confirmed they fit, though performance varies:

  • 60deg Flamingo rubber + ML Crazy Jet barrel
  • 70deg Flamingo rubber + TNT barrel (bridge removed)
  • 60deg G&P VSR rubber + Prometheus AEG barrel
  • 60deg TM VSR rubber + R-hop Prometheus VSR barrel
  • 70deg ML Autobot rubber + ML Crazy Jet barrel (overhops 0.45g ammo)
  • 60deg ML Autobot rubber + ML Crazy Jet Barrel
  • 60deg PDI rubber + R-hopped PDI barrel
  • Laylax purple rubber + Laylax 6.03 barrel
  • 60deg ML Monster rubber + Laylax barrel
  • 60deg ML Delta rubber + Laylax barrel

PLEASE NOTE: Do not install the metal C-clip on the hop rubber that comes with Maple Leaf hop rubbers. It is not necessary and will cause cycling problems as the grip on the nozzle will be too tight.

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