These new billet block adapters allow the use of a big block Chevy electric water pump on the GM LS engine. These adapters feature (2) -12 AN O-ring female outlet ports for routing coolant back to the radiator. The 1/8 NPT port on the sides of the adapters allow a convenient hook-up for the steam tube outlet (eliminates modification of the radiator or water pump when installing the steam tube plumbing). This part includes the two block adapters, gaskets and mounting bolts. Billet Aluminum Block Adapters for GM LS Engines. (2) -12 AN O-Ring Female Ports (Outlet on Each Side of the Block). 1/8 NPT Female Ports For Easy Connection of Steam Tube Plumbing. Includes Gaskets & Mounting Hardware. Use AN Plumbing for the Coolant Return to the Radiator. Ideal for Use w/ Most Electric Water Pumps for Big Block Chevy. Recommended for Use w/ the Following Water Pumps: Frostbite #s (22-113, 22-114, 22-126, 22-133, 22-134), or Mr Gasket #s (7022G, 7022BG). Adapter AN Size (A). 12 AN Female O-Ring. Adapter NPT Size (B).