Solid Rings Home » Solid Rings Cast Iron Frame & Cover Specifications SIZE TYPE WALLS HEIGHT 20" I.D. Plastic -- 6", 12" 24" I.D. Plastic -- 6", 12" 32" O.D. Concrete 3.5" 12", 18", 24", 36" 3' O.D. Concrete 3.5" 1', 2', 3', 4' 4' O.D. Concrete 4" 1', 2', 3', 4' 6' O.D. Concrete 4" 1', 2', 3', 4', 5' 8' O.D. Concrete 4" 2', 3', 4' 10' O.D. Concrete 4" 2', 3', 4', 5' 12' O.D. Concrete 4" 2', 3', 4', 5' Detention Tank Click here for other statistical information.