In piping and tubing-based systems, a ferrule is a small component used to seal a compression fitting assembly. Such compression fittings are necessary elements in a large variety of tubing-based applications, including plumbing, gas lines, and chromatography.
The front ferrule creates a seal against the fitting body and on the tubing outside diameter. As the nut is turned, the back ferrule advances the front ferrule and radially applies and effective tube grip.
