3/16″ inside diameter 7/16″ outside diameter food-grade vinyl tubing. 3/16″ is the best size for most beer lines under 9′ in length. Ideally, 5′ provides the correct restriction for serving beer in the 8-14 psi range.
3/16″ line provides 2.2 lbs of restriction per foot. Ideally pounds of resistance should equal pounds of applied pressure. 3/16″ line holds 1/6 of an ounce per foot. Made from PVC. 7/16″ OD.