Proper selection, handling, and installation of tubing, when combined with proper selection of FITOK tube fittings, are essential for reliable tubing systems. The following variables should be considered when ordering tubing for use with FITOK tube fittings:

  • Surface Finish
  • Material
  • Wall Thickness

Surface Finish

Surface Finish is very important for proper sealing. Tubing with any kind of depression, scratch, raised portion, or other surface defect will be difficult to seal, particularly in gas service. (See below for a detailed explanation of Gas Service).


Metal tubing material should be softer than fitting material. For example, stainless steel tubing should not be used with brass fittings. When tubing and fittings are made of the same material, tubing must be fully annealed.

Wall Thickness

FITOK tube fittings have been repeatedly tested in both the minimum and maximum wall thickness, FITOK tube fittings are not recommended for tube wall thickness outside its range.

Gas Service

Gases (air, hydrogen, helium, nitrogen, etc) have very small molecules that can escape through even the most minute leak path. Some surface defects on the tubing can provide such a leak path. As tube outside diameter (O.D.) increases, so does the likelihood of a scratch or other surface defect interfering with proper sealing. The most successful connection for gas service will occur if all installation instructions are carefully followed and the heavier wall thickness of tubing on the accompanying tables are selected.

If you require any more information on the FITOK tube we have to offer or any other products FITOK have to offer then please contact our sales team: or call 01942601209.