1, mud pump piston assy 2, parts: tube, plate ,snap ... steel alloy 4, NBR /PU piston cup Mud pump piston assyconnected with piston rod, reciprocating working in mud ... pump liner Specifics: external diameter 4-1/2"----7 ... 1, made by NBR (Nitril rubber); bearing tempreture: under 120 centigrade working life: 200 hours Oil resistance, acid-alkali ...