New Proform harmonic balancer cover.  This cover sandwiches between the harmonic balancer and crankshaft pulley on 3-bolt balancers with a 6 3/4" OD for 305-350 CID Small Block Chevrolet engines.  This cover is 1.375" wide, made from aluminum (black), and has etched timing marks from 0 to 60 degrees BTC.  The timing marks are designed to be accurate for 6 3/4" bolt on timing tabs.  Universal applications. ***These covers ONLY FIT the balancer size listed!  They do not work with smaller, nor larger diameter balancers!