This 3/8 inch OD x 1/4 inch OD AquaLock(TM) mini reducing coupling works with plastic or soft copper tubing. It is easy to install, no tools or tube inserts are required. The fitting can be used for hot and cold water applications. The unique O-ring guide feature provides a zero-leak connection. Unlike barb fittings, this fitting joins the tubing on the outside, increasing the flow capacity. After a connection has been made even under maximum pressure, the tubing is able to swivel, making the fitting ideal for vibrating and dynamic applications.