These units have everything you need to make a great learning center. #163045 includes two melamine dry erase surfaces, measuring 29-1/2"W x 43"H, a storage tray, two full-length marker trays, 4 storage tubs, and a wire book rack. Everything you need for lessons is right at your fingertips! The #163021 offers all the same features, but without storage tubs. Each cart has casters making it easy to go with from room to room or station to station. Carts fold for compact storage. A dry erase surface on both sides of the unit makes it ideal for two teachers to give simultaneous lessons. Ships UPS.