CTA Tools 2101 Oil Pump Primer compatible with GM is designed to prime the lubricating system of new and rebuilt engines. It works by sending oil to the internal moving parts before the first start. The 2101 should be used with a 3/8-inch or 1/2-inch reversible drill. Heavy-duty construction allows for strength and durability. California Prop 65 - Warning, This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.