Exclusive polyester bristles with bend recovery. Side bristles have soft upper bristles to coddle the soft upper shoe, while the stiff lower bristles work on the lower portion of the shoe. A scraper bar removes heavy caked mud easily. Bottom bristles are extra stiff to clean spiked and spikeless shoes equally well. The brush blocks are constructed from heavy-duty polypropylene that will not rot. This is the ultimate shoe brush at an incredible price.