fluid end assemblies for pumps and replacement parts therefor all for use in the oil drilling industry; metallic and non-metallic expendable parts for pumps, namely, seals, gaskets, and valve inserts, all for use in the oil drilling industry; metallic and non-metallic replacement parts for pumps, namely, valve seats, pistons, liners and rods all for use in the oil drilling industry; valves and replacement parts therefor, all for use in the oil drilling industry