These drawer slides are being sold at a big discount because they have a defective "bump" roller. The material used in this roller we found to be defective and after a few passes , it just falls apart and will need removed. The good news, if there is any, is that this part is mostly unimportant to the weight capacity and the function of the drawer slide. The drawer slide is completely usable since this part does not support any weight or have any function other than to create a little "bump" pause as the drawer slide extends. If it wasn't there to begin with, you would never notice anything wrong.
If you find anything else wrong with these, we will give you your money back
Side Mount Drawer Slide - 20" - Black - Full Extension - 150 lb Length 20 inch Black Full ext. ball bearing 150 lb. These slides come in pairs with a bracket that attaches to drawer for easy drawer removal. Liberty Hardware