Used with 3-5/8" big bore pistons that use .078" (2.0mm) compression and 3/16" (.186") (4.75mm) oil rings. Std cyl. bore: 3.625" (92.075mm). 1st ring: 2.0mm. 2nd ring: 2.0mm. oil ring: 4.75mm. Note: When 3-5/8" S&S pistons are used you should; in practically all cases; use the Hastings rings for S&S pistons that are mentioned as ''S&S 3-5/8 Big Bore''. These come with 1.6mm compression rings and 4.0mm oil rings. Check before you order. 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.)