The forging design produces a stronger piston than most standard pistons for the ultimate in performance. All Howards HRC Racing Pistons are forged from 2618 billet bar stock and then heat treated and aged to a T61 condition (2618-T61). This material has less than 1% silicon particulate content. High silicon content pistons (forged from 4032 or MS75) will not stand up to the most extreme stress placed on many racing pistons. Simply stated, adding sand to the aluminum only makes it more brittle. Another advantage of 2618-T61 over the high silicon pistons is the ability to keep its shape under extreme pressure and high RPM's. "Skirt Shrinking" is not a problem with Howards HRC Racing Pistons. All HRC pistons are machined on the most modern CNC equipment in the industry. The design of the CNC turned skirts allows these pistons to work properly under intense heat and severe side loads without scuffing or splitting the cylinder walls. Dome pistons are designed with radiused domes, eliminating sharp edges and "hot spots". The valve pockets are built to handle large cam profiles and oversized valves. Forced pin oilers, accumulator grooves and lock removal indents are standard. Sets include lightweight .150" wall, heat treated aircraft quality wrist pins. Double spirolox are standard.