Type:1 Acme Nut Pigtails are used with Double Stage Automatic Changeover Regulators for two cylinder systems or Standard Double Stage Regulators with "T" check connections. UL listed assemblies, CSA approved hose. Hang tagged for store display. Safety features: Excess flow device: Limits gas flow in the event of hose rupture or accidental disconnection. Thermofuse: A heat sensitive plug, which shuts off gas flow if temperature reaches above 240 Degree F. Type 1 ACME Nut Pigtail : 1/4 Inch Inverted Flare x 12 Inch Pigtail.