The B&G Black Plastic Tank Bottom TB-1 (22049477) is designed only for use with the 1 gallon tank since the 2 gallon tanks do not come with the carpet protector bottom. B&G advises that the 1 gallon tank is best for indoor applications, so this is why they do not have the protector rings on the larger tanks. However, if you would like to purchase the tank bottom for your tank, the diameter of the 1 gallon and 2 gallon tanks are the same.