Our LowPro series overflow are designed for use with pre-made or on one of our Custom Aquariums. Our 20 inch version is made out of 1/4 Cast Acrylic and built in the USA in our Facility. The Front unit measures 20 x 1 3/8 x 5 3/8 tall with a removable top shown . The Rear unit measures 20 x 3.5 x 6.5 tall with a full top for strength and a removable lid. The unit is drilled with 3 x 1 inch bulkhead holes for a bean animal system and come with the two 1 1/2 through wall bulkheads.