As we designed the slam ball/wall ball shelf, from the steel tubes we didn't imagine those shelfs could be used also for storing other larger equipment. Then we visited one of our customers, who had a genius idea, and stocked the bumper plates on the shelf, one against the other, just like books. Why didn't we remember that?! The only problem was, that he had difficulties taking down the bumper plates that were stacked in the middle, so we came up with a small invention – The Bumper Spacer. Mount it to both shelf tubes and use it as a barrier between the bumpers, so you can easily stack them by weight.