These forged 3-7/8" big bore pistons are compatible with stock or S&S Super Stock® cylinder heads in Harley-Davidson® Twin Cam 88® and Twin Cam 88B™ engines. These pistons are designed to increase displacement of stock Twin Cam 88 engines to 95" and have a 5.3cc "pop up" dome for a slight compression increase. Piston weight is virtually identical to that of stock pistons in 88 motors, so re-balancing the stock flywheels is not necessary when installing these S&S pistons. 3-7/8" bore, standard size.