CowCow B01 Dynamic BlowBack Unit - Silver
A Great Blowback Unit, we have personally been running these for years.
Unlike the B02 (Piston Head Version) these come with O-rings which are far easier to achieve good seals to your nozzle.
We use these with the AIP nozzles and work flawlessly
Will fit 5.1 and 4.3 variants, includes 3 different size O-rings
Don't forget to pick up some spare Nozzle Springs too, you will need them - trust me!