Beeman P17/Marksman 2004, complete teardown/rebuild.Orings:#006 1/8"ID X 1/4"OD X 1/16"CS: Valve stem tip#008 3/16"ID X 5/16"OD X 1/16"CS: Valve plug#009 7/32"ID X 11/32"OD X 1/16"CS: Breech2.5mm X 20mm exact metric replacement: Piston #117 13/16"ID X 1"OD X 3/32"CS: Piston, Tighter fit