Universal Low / High Baking Rack Set for Microwave / Convection Ovens Universal high / low metal baking rack set for combination microwave / convection ovens. The high rack diameter is 12 7/8 inches, the height is 4 1/2 inches. The low rack diameter is 12 5/8 inches, the height is 2 1/8 inches. The three legs are rubber tipped so it can be used with a glass or metal cook tray.