Heavy-duty Non-corrosive black plastic. Inside Dimensions: 12-5/8 inch x 7-1/4 inch x 8-1/2 inch (WxDxH). Fits 27/27M Series Batteries Heavy-duty non-corrosive black plastic Install with number 10 screwsMeets ABYC standard E-10 and U.S. coast guard requirements Includes adjustable-height crossbar and two retaining bolts