The coupling is used to connect one section of 5/8 in. supply tubing to another section of 1/2 in. supply tubing or dripline. With the increaser/reducer coupler, simply insert the tubing end inside the color coded 5/8 in. green X 1/2 in. black compression ring, where an internal barb compresses into the tube to hold it in place. Made for durability, the compression fitting is made of acrylonitrile butadiene styrene ABS treated with UV inhibitors to prevent cracking.