These Wiseco Big Bore kits are developed for Twin Cam (1450 cc) models. The use of these 4" bore pistons with stock 4" stroke enlarges the capacity of your Twin-Cam engine from 88 to 100 Cubic Inches (1650 cc). The 4" bore kits must be used with cylinder sleeves in your stock cylinders. Sleeves are not included but must be ordered separately. The 4 1/8" bore kits will even give you a 107 Cubic Inch displacement (1752 cc) and must be used with 4 1/8" bore cylinders that must be ordered separately. Both the 4" and 4 1/8" Big Bore kits give a 10.5:1 compression ratio when used with stock cylinder heads, providing maximum torque and throttle response. Kits contain a pair of Wiseco forged pistons, a Hastings ring set, chrome wrist pins and circlips.