This battery box is specifically designed for use with Optima D31 batteries which measure 12-1/2”L X 6-1/4”W. Due to its large size we use four (4) stand offs to hold the battery in place. The box is machined from 3/8" billet aluminum and includes 5/16” mounting holes in the bottom (mounting fasteners not included). These battery boxes are finished to perfection like the rest of our products and are available in a bright polished finish or in a variety of our Fusioncoat or anodized colors.