86-20 Sportster, (except 08-10 XR1200, 10-13 XR1200X)
Computer designed to give a lightweight yet strong piston. Forged out of 4032 low expansion 11% silicon alloy. This design and material along with an Accumulator groove between top and second ring produces a better ring seal. They also feature top land mini grooves which help reduce detonation. Anti-Friction Coated Skirts on piston sets are noted.