Jotco 20 Gallon Tank Topper 24.5" Long Turns any Standard 20 Gallon Tank into a Pet Penthouse!! Dimensions are 24.5" x 13" x 12" Suitable for Hamsters, Gerbils, Degus, Rats and other similar size pets. All Jotco Tank Toppers come fully assembled with no extra steps. Just let down the ramp and set it on your tank!