Bankers Box modular cube shells offer easy access to your letter/legal file boxes (sold separately) during temporary storage or for short-term projects. You won't have to stack or re-stack boxes. Simply slide them into the extra-strength modular shell with steel support frame. The shells fit just about anywhere and stack five units high to save floor space. Durable shells with wire frames clip together vertically and horizontally for stability. File/Cube Extra-Strength Storage Box Shells also feature Quick Setup assembly.