Stainless steel cylinder head (removable with the tool integrated in cheek pad adjustment knob)
SRS piston with specific 90° piston end (steel)
Stainless steel spring guide with thrust bearing
APS 13 mm spring compatible (90 Newton stock spring, initial muzzle energy around 1.5J, with 0.2g bbs, minimum hop up setting), Warning: Not compatible with SBA-SPR-08 (95 Newton spring).