A 3-inch PVC ball cork is a plumbing fitting that is used to control the flow of water in a PVC pipe. It is made of a cylindrical piece of PVC with a ball in the center. The ball can be rotated to open or close the pipe.
PVC ball corks are typically used in irrigation systems, greenhouses, and other applications where it is necessary to control the flow of water. They are also used in some plumbing applications, such as to shut off the water supply to a faucet or appliance.