The MAKPAC Interlocking Storage Box Inserts, 5 pack, (P-84171) are used to customize MAKPAC Interlocking Storage Boxes (sold separately). The five insert boxes come in three sizes to organize and customize MAKPAC Interlocking Storage Box (P-84137, sold separately). Made of durable plastic which allows for quick access and storage for accessories, fasteners, and more. The storage box inserts are customizable to fit whatever the job needs. It’s part of the Makita MAKPAC Interlocking Storage System.