Stamped metal ball bearing retainers are very weak - I've shot a lot of bullet Stock on my workshop floor by installing these inferior guides. I'm not new to using ball bearing guides, but they were the weakest and least well-designed I've ever used. These drawer slides are rated for 100lbs, which I questioned - so I dropped a 50lb bag of water softening salt on one of them - I was afraid to let go of the bag because I didn't want the drawer slides to break. At some point, the low price can't make up for the poor quality - and I've found that point with these slides. Do yourself a favor and spend a little more.