... :Bolts and nuts ,Thread ring ,Upper and lower valve Guide ,Liner End Cover ,Valve Pot Cover ,Cylinder Head ,Cylinder Head Plug ,Liner Seal ... valve-over-valve design reduces the volume in the fluid end and improves the volumetric efficiency.When you order parts, please ... , Pistons, IDECO, National, Oilwell, OPI, Skytop, Wheatley, and Wilson fluid end Assembly