Loose flanges are used together with HDPE polyethylene adapters (flange ends) in water supply, sewerage, and natural gas installations. Loose flanges slide onto HDPE connection fittings and allow joining with valves or parts that connect with flanges. Material: carbon steel. Reference standard SR EN 10921-1 Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories, designated by PN. Part 1: Steel flanges. Loose steel flanges have standardized dimensions except for the inner diameter which is adapted to the size of the flange stub end (Waterkit). Explanation of terms in the designation D= outer diameter of the flange stub end with which the flange is compatible DN= nominal diameter of the flange according to SR EN 1092-1, SR EN ISO 6708. Compatible with: PE100 PN16 flange stub ends, article codes 44411% and 45411%. Flat rubber gaskets, article codes 44799%. Bolt sets with nuts and galvanized washers, article codes 44798%.