All Berry's ammo boxes are made from high impact polypropylene for increased strength against cracking, chipping, warping, expansion, or contraction. Our model #001 100 round boxes feature our new, stronger, flip-top design, allowing the securing of ammo storage with easy one-handed operation. Along with a translucent lid, they now come with a black base for increased strength and a clean look. They are stackable, they carry a lifetime warranty, and they are made in the USA.