Black Wheel ShMITT: The black foam is very coarse. The black ShMITT is best used for scrubbing wheels, tires, and the undercarriage. It can also be used for stubborn spots on interior vinyl, but not if it’s already been used on the tires or undercarriage. This could cause cross-contamination. Our recommendation is to reserve this mitt for cleaning wheel wells and tires. The rugged foam will easily dislodge tar and grime using your regular car shampoo and water, or a degreaser, like DP Cleanse-All exterior surface cleaner.