124" kit for 99-17 Twin Cam 4-1/4" bore 4-3/8 stroke 11.2:1cr (w/ 86cc heads); 10.4:1cr (w/ 95cc heads). Aerospace-grade all-aluminum cylinder with nickel-silicon-carbide (NSC) electroplated bore No sleeving allows for larger bore sizes NSC-plated cylinders have less friction for increased horsepower, lower engine temperatures and a longer lifespan Monster big bore kits will require case boring Includes pair of all-aluminum NSC-coated bore cylinders, custom-forged pistons with high-tension rings specifically designed for NSC cylinders and a head/base gasket set Replacement gasket sets available separately Upgraded cylinders studs and head bolts recommended Made in the U. COLOR/FINISH GRANITE BORE SIZE 4.250" DISPLACEMENT 124" STROKE LENGTH 4-3/8.