Smooth flowing symmetrical dome for excellent flame propogation. Dome requires no de-burring or preparation. Designed for use in all common 23° heads. Non-silicon alloy for superior strength in high cylinder pressure applications. Symmetrical dome and valve reliefs for universal installation. .927'' x 2.750'' x .150'' straight wall carbon steel wristpin (130g) included. 1/16, 1/16, 3/16'' ring grooves.