How are pistons engineered so that thermal expansion doesn't cause too much friction or break the piston's airtight seal? - Quora
main parts of engine || piston working || piston parts and their functions - YouTube
APS Polyamide Explosive Bearing Piston Head for Standard Airsoft AEG Gearboxes, Accessories & Parts, AEG Internal Parts, Piston Heads - Evike.com Airsoft Superstore