Brushes of various stiffness are available for your 15" TRIO machine. Each TRIO has 3 brushes total, including two outer brushes and one center brush. All brushes should be same color/stiffness for best results. Depending on the application, different brushes are appropriate. Our brushes are color coded for easy identification. - WHITE - Soft bristle for use on wool, staple cut or extra deep pile. - GRAY - Medium/standard bristle for use on commercial grade carpets, including level loop or low cut pile. - BLACK - Stiff bristle for use on matted commercial grade. Not for regular use, only for periodic heavy pile lifting. Note: Price is per brush. The machine requires 3 brushes.