Plunger: Stainless Steel. Plunger seals: Oil Seals. ►Hole Distance to hole is 2 9/16". ►Key width 3/16". ►Depth 2 5/8". ⚠ Will not fit Shafts By Older GC160 Honda Engines. This Pump is ONLY for Horizontal Engines with a 3/4" shaft!