A PVC 20mm Grey Straight Connector fitting is a type of plumbing fitting used to connect two pipes in a straight line. The "PVC" refers to the type of plastic the fitting is made of, which is known for its durability, resistance to chemicals, and low cost. "20mm" refers to the size of the fitting, which is the inside diameter of the pipe it will fit on. The "Grey" is the color of the fitting, this color code is use to identity the material and also indicate the pressure rating of the pipe fitting. The "straight" connector refers to the design of the fitting, which is a simple tube shape, connecting two pipes end to end, in a straight line. This type of connector fitting is typically used in irrigation, plumbing and pool or spa piping systems to connect two sections of pipe together and allows for a continuous flow of water through the pipe.