Carpet Shampoo Brushes On brushes 14" diameter and larger, the two outer rows are heavier to scrub the carpet and flex the pile while the softer inner rows “massage“ the dirt from the carpet for a deeper cleaning action. A low cost alternative to nylon for situations that call for less frequent use. Ideal for the rental trade. Bristles are slightly stiffer than nylon. Carpet brushes must be broken in as described before use on carpets: 1. Mount the brush on the floor machine. Follow ALL instructions included in your owner‘s manual. 2. Find a rough textured floor surface, preferably unfinished concrete. 3. Operate the machine on this surface. Run the machine DRY for approximately 15-20 minutes. The brush fibers will take a slight set or lean in the direction of machine rotation. 4. Rinse the brush to remove any dirt caught when running machine. The brush is now ready to be used on carpeting. Optional clutch plate 4101B_NP-920 Malish: Universal Clutch Plate :