Melling select performance oil pump wet sump, internal, High volume, High pressure spring, 25% increase in volume. Fits small block chevy 265-400 CID. Comes assembled with high pressure relief spring, standard relief spring also included. Inlet diameter 5/8″, hardened steel gears and cast manganese phosphate coated housing, “shark tooth” helical asymmetrical gears, intermediate shaft included. Please e-mail with questions.