This heavy duty pack box is made to with stand years of back country packing and is a certified Bear-Resistant Container. The box is designed with durability and performance in every aspect. The sides are curved to fit comfortably on your pack horse or mule. Each box comes with blended poly-nylon straps for extra strength in attaching the boxes to your pack frame and easy length adjustment. The lid has eight 5/16" wing bolts to secure it to the box and keep animals out.