***LIMITED ITEM PLS ALLOW 4 BUSINESS DAYS HANDLING TO SHIP*** Keith Black piston set .010 oversize and is for a 3.875 inch bore. Piston set has a compression ratio of 9.3:1 and includes rings. The Keith Black 390 hypereutectic alloy is cast in a permanent steel mold which makes it possible to build a light weight piston that makes more power and uses less fuel and lasts longer. Pistons are .010 oversize for a 3.875 inch bore and has a 9.3:1 compression ratio. The low heat transfer of the alloy keeps the skirts cool so piston expansion is minimal. The combination of a low heat transfer piston alloy and high compression ring placement increases power and economy. The high ring placement alone reduces detonation and increases the top ring temperature. **Note: Run engine at moderate speeds for at least 500 miles avoiding excessive running in lower gears in order to properly break-in new pistons and rings. FITS HARLEY: 2007-2017 FXST, 2007-2017 FLST, 2007-2017 FXD, 2007-2016 FLT, 1941-1977 FL, 1971-1977 FX, 0- Replacement, for Wiseco pistons 2017-UP FLT,