Abstract: A reciprocating compressor carries suction valve apparatus on its piston in the form of a sheath. The sheath is retained and guided for motion both in conformance with and relative to the piston on which it is carried so as to accommodate both the flow of suction gas into the cylinder in which the piston-sheath combination is disposed and the compression of such gas therein. Retainers are disposed in the ends of the piston's wrist pin and have end faces disposed in accommodating apertures in the sheath. The configuration of the retainer end faces and the sheath apertures in which they are disposed act to limit and guide the movement of the sheath with respect to the piston.