Eastman 60023 Thermal Expansion Tanks, 4.5 Gallon, White Capacity: 4.5 gallons of water with a factory pre-charged pressure at 40 psi Dimensions: 16-inch x 11.1-Inch x 10.9-Inch with 3/4-inch mip connection Material: it has a high-quality butyl rubber diaphragm and grade 304 stainless steel fittings for long-lasting performance Design: the tank is designed to prevent hot water from back flowing into the cold water line, or escaping through the pressure relief valve Options: this thermal water expansion tank is available in varying capacity of 2 gallons and 4.5 gallons of water; choose as per requirement