The Rein Expansion Tank Blind Plug - CHM0522 is a small, circular plug used to seal off the opening of an expansion tank. It is made of durable materials and is designed to fit snugly into the tank's opening, preventing any leakage or contamination. This blind plug is an essential component of the expansion tank system, ensuring proper functioning and preventing damage to the tank or surrounding components. It is compatible with a variety of expansion tanks and is easy to install. This product is a reliable and cost-effective solution for maintaining the integrity of your expansion tank.