Std cyl. bore: 3.498" (88.85mm). 1st ring: 1.6mm. 2nd ring: 1.6mm. oil ring: 4.75mm. Tech tip: Piston grooves vs piston rings. It''s not difficult to determine if a Hastings piston ring set will fit a certain piston. You should measure the height of the piston groove in the piston itself. The 2 top grooves will be for compression rings; the lower groove will be for the oil ring. In most cases Hastings oil rings are of the low tension 3-piece flex vent type. Ring heights are listed for reference. Tech tip: Piston oversizes. For each oversize cylinder diameter will increase with .010" (0.254mm). The standard bore of the cylinder is listed for reference. (Tech tip information provided by Hastings Manufacturing Company; Inc.)