The pigtails are specially designed to meet the requirements of NFPA for Hospital medgas manifold systems. The major feature being NFPA’s requirement for permanent affixed ends to avoid cross connection through modification or switching of the nut and nipple to hook up a different gas than a system was designed for. The other requirement is a mandatory copper pigtail for use in high pressure oxygen service. Some states also require that because Nitrous Oxide is an oxidizer, copper is also required.