This fitting works perfectly for installing 1 1/2 suction and return lines in a wooden hot tub up to 1 1/2 thick (it could be a bit thicker, but 1 3/4 would be pushing the edge). The price is outstanding as these fittings are hard to find. The inside facing is threaded and works well for adding a screw in skimmer to the suction side. Outside is a slip fit. This unit includes the tightening nut and the inside has a rubberized ridge that functions like a gasket. Great product if you are adding a circulation and/or heating system to a wooden tub.
Rating: [5 of 5 Stars!]