Each mailbox is designed with an individual name tab for each slot. Use tab to organize materials by student, subject or class period. Mix and match the three sizes of mailboxes to get the right number for your class size. The slot sizes are 3"H x 10"W x 12-1/2"D. Recycled and recyclable. Mailbox measures 16-3/8"H x 31-1/2"W x 12-7/8"D.