... pump piston assy 2, parts: tube, plate ,snap ring and cup 3, material: carbon steel alloy 4, NBR /PU piston cup Mud pump piston ... assyconnected with piston rod, reciprocating working in mud pump linerSpecifics: external diameter 4-1/2 ... "----7-1/2" inner hole: diameter 1-1/2" & 1-5/8" Piston cup ...