Dormont 30 Series- Corrugated, stainless steel connectors with special Supr-Safea® design to increase flexibility. Maximum service and safety, approved for indoor or outdoor use. Perfect for range and furnace connection. AGA and CGA approved. 3131 Series: 5/8in. O.D. x 1/2in. I.D. 1/2in. MIP x 1/2in. FIP Connectors.