Attaching to an existing21"d x 30"w starter solution, these chrome wire shelving add-on units bring more storage to your space without the need for a completely new system. Pairs with existingstarter unitto extend length of shelves for more storage space Durable chrome-plated steel construction 800 lb capacity shelves can be adjusted easily in 1" increments along posts Made for indoor use, dry storage only S-Hook 2-Packrequired per extra shelf To securely set or quickly remove shelves, tap their corners with a rubber mallet.BUY HERE. View ourWire Shelving Size Guideto see actual outer and inner dimensions.