- 21 Inches x 21 Inches x 18 Inches. - Places Gas Water Heaters 18 Inches Above Floor As Reqired By The National Fuel Gas, And Plumbing Codes. - 18 Gauge Galvanized Sheet Metal Holds Up To 50 Gallon Water Heaters. - For use with gas water heaters having a diameter of 22 inches or less and a rated capacity up to and including a 50 gallon water heater - Easy instructions.