Sold by the foot. Use this size for gas line applications. Also used for long draw beer lines over 25'. Technical Specifications: 5/16" line provides .40 lbs of restriction per foot. Ideally pounds of resistance should equal pounds of applied pressure. 5/16" line holds 1/2 of an ounce per foot. Made from PVC. Quantity ordered will be shipped as a single uncut length. Maximum length available is 100 ft.