Brass Threaded Flanged Hexagon Basin Waste Backnut - 1 1/2" BSP. Brass-flanged back nuts are perfect to use in your central heating and Hot or Cold water supplies. Backnuts are easy to install and require no solder to make connections. Ideal for successfully securing ball valves, toilet handles, and tank connectors to toilet cisterns and tanks.Technical Specifications: For Basin Waste (Due to Size) Finish - Brass Flange Backnut Hardwearing Outer Diameter - 55mm Hexagon Backnut Thickness - 10mm Spanner Size - 51mm Pack of 1 Unit Size - 1 1/2 Inch or 1 1/2" BSPPlease Note: BSP threads are 1/4 inch larger than that stated in BSP terms.