i broke this piston after only 200 rounds or so! don't get me wrong, this was a great piston for my ICS M4. i basically bought a new upper gearbox and put it together using all systema parts: this piston, the systema energy cylinder set (cylinder, air nozzle, piston head, etc...), systema area 1000 metal spring guide, area 1000 tappet plate, and a systema M130 spring!
how the last 2 teeth of this piston broke i have no clue. supposedly this was meant and designed to be lightweight and strong, but a M130 spring and all stock parts of the lower gearbox (ICS PCR-97 stock gears and motor) managed to break the piston. all in all, it was a good piston from the start; all 200 rounds i shot were in the 420+ fps range (combination of the upper gearbox i put together, mad bull 3-in-1 metal hop-up, and mad bull 6.03 mm tight bore inner barrel)
compatible with ICS parts
strong (to a point i guess)
not strong enough
possibly meant for M120 springs and lower
the metal part should be at the end where the piston teeth and gears make contact