Our beautiful 6061 billet aluminum crank sensor hole plugs include a Viton® Fluoroelastomer O-ring and M6-1x16 hex flange bolt and are accurately machined out of 6061 aluminum. Fits small-block chevy (SBC) Vortec timing cover, LT1 timing cover, and Vortec big-block chevy (BBC) timing cover. V6 and V8 compatible. Not for use with the 2007-newer Vortec engines.