Tube Fittings are designed, manufactured, and quality controlled to be totally "interchangeable" with the Swagelok® brand of tube fittings.The double ferrule design, with the staged sequential swaging action of the ferrules during make-up, Back ferrule make a grip on tube & front ferrule work as sealing on tube, compensates for the variation in tubing materials, hardness, and thickness of the tube wall to provide leak-tight connections in an extensive range of applications.