96-103″ big bore conversion kit. 9:1 compression ratio. Converts the stock 96″ Twin Cam to 103″ with stock heads. Stock cylinders must be bored from 3 3/4″ (3.750″) to 3-7/8″ (3.875″) to accept the 103″ big bore pistons. Comes with reversed dome forged pistons, Hasting rings, circlips and wrist pins.