I knew what I was getting before I ordered this item because I had one of these that I bought at a brick and mortar store in the past. Lok carefully at the picture and you will see that it is four black rails that extend to fit under the sink. You can then add or remove five - six shelf pieces to make up to two shelves under the sink. The shelf pieces snap on and can slide back and forth along the rails. You can also adjust the height of the shelves by moving the rails up and down. They are held by plastic hand screws on each side. I will say that it doesn't magically sole your space needs under the shelf, but if you think it out a bit, you can almost always increase the amount of storage space under your sink.