This convenient Vacuum Line Barb Fitting assembly is designed to be inserted into a silicone coupler and provide a leak-free seal. Simply punch a 8mm hole into your silicone coupler and pop the fitting in place. Each kit includes a CNC Machined Aluminum Barbed Fitting, Lock Nut, Washer and O-Ring seal. For use with Vibrant Performance 3/16 (4mm) I.D. Vacuum Lines.