Delivery Quantity: 4 Pieces Premium Material: The threaded winter pool plug cap is made of high quality plastic and rubber, it is strong and reliable, not easy to break and rust, and can withstand old temperatures without slipping or shrinking. Practical: Each plug is equipped with an O-ring to ensure a tight seal between the plug and the pipe. Once the water comes out, simply screw the plugs into all the returns and drains, threaded pool return pipe plugs help keep the pipes from breaking easily and are easy to handle. Application: These swimming pool winter expansion plugs are ideal as antifreeze plugs for above-ground and in-ground swimming pools in winter, and can be used as pipe plugs to plug skimmers, return lines, and cleaning pipes to prevent water from entering winter pipes and causing corrosion inside the pipes . Appropriate size: The cap size of the threaded pool drain plug is approx. 2.05"/5.2cm, the inner diameter of the plug is about 1.5"/3.8cm, and the outer diameter of the plug is about 1.81"/4.6cm, please confirm the size before purchasing. What's included: You'll get 4 1.5" threaded sump return line plugs, each with an o-ring that's big enough for you to replace for your convenience.