Most boxes for this kind of exercise come in wooden form. The wood material is thick and strong but it may not always be enough for heavy athletes. Their joints can also give way leading to sudden injuries. A steel Crossfit plyo box offers excellent durability and high load capacity. The joints are welded together for excellent bonding.
They also come in a trapezoidal shape rather than a perfect rectangle. This gives them a bigger base for greater stability. You are also less likely to catch the top with your foot which reduces the risk of accidents. There is only one height per unit but you can nest several of them for easy storage.
If you are seeking to invest in high quality plyo boxes, then this is a good option. You can do intense workout without fear or hesitation thanks to their awesome toughness.