Parts of oilfield wellhead machines, namely, fluid ends, and parts for fluid ends, in the nature of valve seat seals, seats, inserts, valves, springs, discharge covers, discharge cover seals, suction valve stops, suction cover, gauge covers, hammer union seals, gauge retainers, plungers, plunger clamps, discharge flange nuts, discharge flange spring gaskets, discharge flanges, and discharge flange seals