(Click to see larger image) This quick-connect tube fitting adapts from 3/8 NPT female threads to 1/4 inch OD tubing. It grabs the outside of the tubing securely so that it holds more tightly as pressure in the tube increases. Unlike a barb fitting, it allows for flow through the complete inside diameter of the tubing without adding a restriction point.

To install tubing into a quick-connect, push it all of the way in. There will be a few millimeters without any resistance and then a few millimeters more where you feel resistance as the tube pushes in and stops. When you try to pull out the tubing, the colored ring extends and the fitting bites into the OD of the tubing. To remove tubing from a quick-connect, push and hold the colored ring in toward the fitting while carefully pulling out the tubing.