A piston is a component of reciprocating compressors located in a cylinder and made gas-tight by piston rings. In a compressor its purpose is to transfer force from the crankshaft to the piston for the purpose of compressing the gas in the cylinder.

The ERVOR G04/G05/G06/G08 piston is a unique monobloc piston with the low and high pressure piston axialy opposed and united with 4 arms.