This is a 3/4\ NPT (National Pipe Thread) check valve, specifically the model 32021 used on Clean Burn waste oil heater systems. Its job is to go on the pickup line inside the oil tank to make sure oil only flows one way – to the burner – and doesn't drain back. This is a crucial little part for keeping your heater running smoothly and preventing airlocks. It's brand new and from Clean Burn, the leading brand in waste oil heating. If your old valve is stuck or leaking, replacing it can solve a lot of common problems. A simple but important maintenance item for anyone running a Clean Burn system. Keep your shop warm and your heater efficient with this genuine-style replacement part.