4-5/8" stroke with 8-1/2" diameter flywheels. Balanced to 1035 grams total piston weight. Stock replacement for S&S engines; custom for OEM engines. No hassle in rebuilding or getting the right parts; it''s all here in one package. These are exactly set-up like the flywheels used in current S&S production engines. Note: Engines with strokes exceeding 4" may require S&S piston oiling jets and piston to jet clearance notches in the piston skirt to avoid contact. Note: S&S crankpins allow the use of replaceable bearing races in the lower end of the connecting rods. The first generation of S&S crankpins; in use up to 2012; were 1.500" diameter. The second generation crankpins; in use since 2013; have the larger 1.671" OEM diameter crankpins. Now S&S & OEM crankpins are identical in diameter so now S&S parts can be used to rebuild stock H-D flywheels; something that previously was not possible since H-D rebuild parts were; and are; not available. Note: Following is regarding 03-17 models. S&S has designed these flywheels to work with a Timken style sprocket shaft bearing; they will fit stock 99-02 model year and all S&S cases without modifications. Stock H-D 03-17 Twin Cam engines use the same sprocket shaft roller bearing as is used on the pinion shaft; a cost saving but weaker solution. It is possible to use the stock weak 03-17 sprocket shaft bearing kit (OEM H-D 24004-03B) with S&S flywheels in 03-17 stock cases. However; S&S feels this roller bearing will not take the