High density urethane brush inserts double the capacity for storage and securely guarantee no more crushed brush hairs. Each insert has 3M industrial strength adhesive on back. These are a direct replacement for the stock springs in the Mack Brush brush boxes and can also be used in any brand of box you may have. For Mack's small brush box (6 3/4" x 5") you can fit one insert- for the medium size (10 1/4" x 3.5") you will need two- for the largest Mack Brush brush box (14" x 5") you can fit three.
Each brush box insert measures 4.75"long x 1"wide x 3/4" high.