Spa Heater Tailpiece for industry standard 2" buttress thread x 2" Socket for 2 inch PVC pipe size.1 per pack. This PVC coupling connects the hot tub heater to 2 inch PVC pipe fittings, has 2" female socket to fit any 2" fitting or 2" pvc pipe. Features o-ring groove for standard o-ring or ridged gasket. Measures 3-1/16" outside diameter of threads, approximately. Sold as a single tailpiece with one o-ring.