This standard aims to set the dimensions, technic and operating specifications, as well as testing to be met by stainless steel tubing with stainless steel fittings for joining reception facilities for fixed appliances that use gas as fuel. The flexible tubes with stainless steel threaded connections are applicable for joining fixed individual receiving installations, of fixed or immobilized gas appliances, which use as fuel gases of the 2nd or 3rd families defined in the UNE-EN 437 Standard, supplied to pressures not exceeding 0.4 bar.