(4Pcs Brass 5/16" 8mm Straight Hose Barb Fitting Reducer Adapter. Item included: 4 x 5/16" Hose Barb Fitting. 8 mm( 5/16"). 7) The barbed stems create a tight seal on flexible and semi-rigid hose when used with a hose clamp or crimp sleeve or ferrule (not included).