Bolts on with existing timing cover bolts. It is chrome plated steel, which makes is a better compliment to a chrome timing cover. It also has an adjustable red timing pointer. This allows for better visibility and helps you set your timing more easily. Just loosen the screw, set the pointer to the desired initial timing level, and screw it back down. Then you'll be able to more clearly see if your timing is where you want it when checking your timing. Has markings from 12 degrees before top dead center (BTDC) to 8 degrees after top dead center (ATDC).