Some brewers prefer the narrower 3/16" inch diameter, to minimize foaming by providing more flow restriction in shorter (5' or less) beer lines. 3/16" inner diameter tubing is used in our beer towers, and in all our draft systems. This tubing is 3/16" inner diameter by 7/16" outer diameter. This tubing will fit 1/4" hose barbs if you heat it in hot water before slipping over the fitting.
Note: The reviews below about the tubing being thin where placed when we were selling thinner 3/16" by 5/16" tubing. Thanks to your reviews, this has been corrected and the current tubing is a thicker 3/16" by 7/16". Sold per foot.