1/4 x 3/16 Reducing Union with CaptiveThe 1 4 x 3 16 Reducing Union with Captive Sleeve Nut is a compression fitting designed to connect two different sized tubing lines securely. The reducing union allows for a smooth transition from outside diameter (OD) tubing to OD tubing, ensuring a leak free and reliable connection. The captive nut feature ensures that the fitting remains in place during installation, reducing the risk of losing small components and improving ease of use.