3M 875704 Standard Abrasives MD Mini-Brush, 4-1/2 in x 4 in x 5/8-11 FB051 15-46 A VFN Medium Density, 1 per case. Our Standard Abrasives MD Mini-Brush features medium density (MD) Buff and Blend material for efficient restoration of original, high-quality finishes on fabricated steel parts. While welds or other imperfections might detract from a fine finish, the original luster can still be salvaged even revitalized and renewed with the help of this abrasive brush.