Applications: ISIFLEX steel pipes/galvanised pipes acording to BS 1387, BS 3601 and BS 3602 · Steel pipes 3/8" til 4" (NS 5587) ISIFLEX-ATU couplings are 100% end-load resistant! Material: · ISIFLEX-ATU couplings have a robust design and wall thickness. All housings are 100% pressure tested. · O- ring is of NBR (for water and gas), and HTB (for gas) · Bolts are galvanized (2 1/2" - 4")