Hastings, 3-5/16" piston rings. +.030"

3-5/16" piston ring set with 3/32" (.09375") gray iron parkerized compression and 3/16" (.186") chromed 3-piece oil rings. Fits 37-48 74" (1200cc) 'U' model Flatheads and 48-52 61" (1000cc) E, EL Panhead models.
Std bore: 3-5/16" (84.138mm).
1st ring: 2.38mm (3/32").
2nd ring: 2.38mm (3/32").
oil ring: 4.75mm (3/16").

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.)