First of all, what you need to understand before ordering. If you have cabinets with a front frame that has gaps on the sides that prevent you from installing rails on the side of the cabinet and you are installing rails toward the back of the cabinet, DO NOT purchase the length for the depth of the cabinet for the depth of the drawer. Most of my cabinets are 23 inches deep from the front edge of the front frame to the back of the cabinet, and all of my drawers are 20 inches deep. Based on the response I received from the seller/manufacturer, I ordered 20" slides based on the size of the drawer. As a result, the rails are a few inches too short to attach to the back of the cabinet. Either add a latch to the back of the cabinets or buy longer slides. This causes the drawer to stall when I pull the drawer all the way out, but it doesn't affect the stability or function of the drawers. There is another option if your cabinet design consists of solid walls with a gap on either side of the drawers. You can add a block to fill the gap, allowing side rails to be fitted at the depth of the drawer. Unfortunately, most double-door closets are open in the middle and won't close. I don't have anything to add filler to. I ended up returning the 20" and ordered the 22" (the available size closest to the depth of the closet, but no more than that depth). The rear brackets allow about 1-1/4" of adjustment, so a 1" difference can easily be accommodated. moderated by brackets.