Dreffco 3/4" x 18" Black Non-Whistle Gas Flex Line for NG or LP Fire Pits For Use Indoors or Out 3/4" Female Flared Fitting Each End. We've Included 3/4" Male and Female NPT Fittings For Your Convenience 18" 3/4" Non-Whisle Flex line is 5/8" OD and 1/2" ID x 15-1/8" Long w/o Fittings There Is a Staggered Pitch Every 2" to Eliminate Whistling Typicall Use Is for NG or LP Fire Features &gt;200K BTU with a 3/4" Connection Hub