活塞头

solid-skirt piston

moisture separation in the reciprocating-piston pump

differential pump (multistage pump, multi-cellular pump, step piston pump)

piston with inserted ring carrier

combination of rotary-piston pumps with oscillating-piston pumps

radial-flow piston machine or pump, variable displacement pump,

hydrostatic engines of reciprocating-piston type with

differential pump (stepped-piston pump)