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.