Replacement for 99-06 Twin Cam models that are equipped with the 95" (1550cc) 3-7/8" OEM big bore kit. Also fits 07-17 Twin Cam 103" (1690cc) engine. Std cyl. bore: 3.875" (98.425mm). 1st ring: 1.5mm. 2nd ring: 1.5mm. oil ring: 2.5mm. 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. (Information provided by Hastings Manufacturing Company; Inc.)