S&S Cycle 2007+ BT 3-7/8in x 4-3/8in Piston Set - Standard

3-7/8" Bore For 103" Engines. Pistons for 103" kits are machined to such close tolerances that it is not necessary to measure the piston. Additionally, the low friction coating on the piston skirt makes taking measurements very difficult. Therefore, hone cylinders to nominal diameter +/- 0.0001" for correct clearance.