Brass Push>Connect Air Brake Tube Fitting, 0.25 Inch Tube OD Run To 1/8-27 Male NPT Swivel Branch, Tee

A clean, square cut matters more than most folks expect with push-connect fittings like this one. The collet grips the tube by biting evenly around the full circumference, so if the end is angled or ragged, you can end up with a weak hold or a slow leak instead of a solid seal. A good tubing cutter gets you there without much fuss. Once the end is clean and square, push the tube straight in until you feel it hit a firm stop. That's how you know it's seated right.

Yes, this Push>Connect fitting is designed for use in air brake systems, and it meets D.O.T. FMVSS 571.106 and SAE J1131 standards, so it's suitable for that purpose. Just be sure to make a square edge cut on the tubing before you insert it.