OPD fittings replace the engine oil pan drain plug and provide a 1/2" NPT connection to complete and simplify the oil change system installation.Groco's OPD series oil pan adaptors complete your U-Lube Oil Change Kit installation. Threaded to match the original equipment plug size for your engine, generator or transmission, OPD adaptors provide a 1/2" NPT connection to complete and simplify the oil change system installation.Machined from brass, models are offered to fit a wide variety of oil pan threads. Locate your engine manufacturer and model in the Adapter List below.OPD Adaptor List