Wire reinforced plastic panels that snap together to make storage cubbies with doors. 13.5 x 13.5 x 17.5 inches deep. These are in pretty good shape, I’m just upgrading to cabinets. They will hold a pretty decent amount of weight:  I've stored extra canned goods, photo albums, etc.  I have two that are assembled into 4x4 units but you can take them apart and re-configure them as needed.  I have these reinforced with cable ties for extra security.  I have additional panels that would allow you to create an additional 8 cubes.  More than 8 additional door panels to swap out if panels get wonky in the future.