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You are ordering from normal stock which is a black hop wheel and red hop unit.

This is a 12-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, 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:

The kit contains 12 parts:

  • KC-VSR Cylinder-Nozzle V5, 7075 CNC aluminium, clear anodised
  • Genesis Hop Unit V4A, 6061 anodised CNC aluminium
  • Diadem Hop Wheel V3, 7075 anodised CNC aluminium
  • 3 x Hop Keys: Arch, Bridge, Flat. 6061 anodised CNC aluminium
  • 3 x Flow Restrictors: Low, Medium, High. 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 hop wheel
  • 1 x 2.5mm knurled steel return spring 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 kit also requires some bedding-in to work properly once installed as all the new parts need time to wear into your gun, as not all KC-02 receivers and trigger mechs are the same due to casting variations of the KJW parts. We recommend plenty of lubrication and manually racking the gun until it draws and returns nicely, cleaning the metal dust out of your receiver regularly. This process should take less than an hour at most. Most people reported only 15 minutes of racking before it cycled smoothly. You're changing the core of your gun for one made of different materials and with much tighter tolerances, so it is not suprising if it doesn't cycle perfectly first time. It just needs to wear in.

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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