These Wiseco Big Bore kits are developed for Twin Cam 96CI (1,550cc) and 103CI (1,690cc). The use of the 3 7/8" bore pistons with stock 4.375" stroke enlarges the capacity of your Twin Cam engine from 96 to 103CI (1,691cc). The 4" bore kits will even give you a 110CI displacement (1,802cc) but must be used with the use of cylinder sleeves in your stock cylinders. The 3 7/8" bore kits can be used in bored-to-size stock cylinders and are also a drop-in for stock 103CI cylinders. Sleeves are not included. Kits are available with classic forged pistons or forged pistons with ArmorX piston coating and ArmorFit skirt coating for reduced wear and auto-adjustment to the cylinder wall. Compression ratio is given for stock or Screamin' Eagle heads. Big Bore piston kits contain a pair of Wiseco forged pistons, a Hastings ring set, chrome wrist pins and piston pin locks.