Keith Black Hypereutectic Piston Kit For Harley Shovel Head Keith Black Pistons are crafted from high-strength 390 hypereutectic T5 aluminum alloy for superior strength and a tighter fit! Features: High-strength, T-5, heat-treated, 390 hypereutectic aluminum alloy Diamond-machined pistons are held to plus or minus one gram weight and less than one-half-thousandth-inch (.0005) tolerances from piston to piston KB pistons can be installed tighter than other pistons. This results in less piston rock and better ring seal Each kit contains two pistons, pins, spiral-lock pin clips and Hastings moly rings Specs: 3.498 stock size 8.3:1 compression ratio