1.Each Fitting Contains the Sealing Glue, No Need Teflon Tape, Easy to Use. 2.Pure Copper Surface Copper-plated Nickel, Stronger and Longer Life. 3.After the Tube is Connected and Installed, Pull the Tube to Make Sure That the Tube 4.Cannot Pull out the Fittings. 4.When Inserting the Tube, It Must Be Inserted into the Bottom of the Fittings. Failure to Insert the Tube into the Bottom May Lead to Air Leakage. 5.Make Sure That the Cutting Surface of the Tube is Vertical, There is No Scar on the Outer Circumference of the Tube and the Tube is Not Oval. 6.Tube Fittings Are Easy To Install, Flexible And Space-saving, 360-degree Rotate Freely, Release Rings Adopt Ellipse Design, Which Can Be Removed Conveniently.