A set of 3 spare nozzle flow restrictors from the Genesis kits.
These also fit the standard KC-02 plastic nozzle.
These are fitted in front of the rocket valve spring in the nozzle, to reduce power output.
They are roughly meant to achieve
- Under 450fps (red)
- Under 400fps (blue)
- Under 350fps (green)
But these are entirely dependant on your barrel length, propellant gas and ammo weight. You will need to do your own testing with a chrono after assembly.