This is a Bore-Up Piston Head by SHS. It is constructed with POM material and comes with thrust bearings.
Bore-Up Piston Head's are only compatible with Bore-Up Cylinders. They will not fit in standard AEG Cylinders.
If you are going to use these Piston Heads in a high rate of fire gearbox, then I highly recommend removing the Thrust bearings. I also recommend using threadlocker on the main screw to secure the piston head onto the piston.