Flagged-tip bristles are resistant to acids and detergents Soft Bristles safe for most surfaces. Staple-set into a sturdy foam block Brush Soft Utility Scrub Green – Short Soft Utility Scrub Brush Green – Short. Bristles are staple-set into a sturdy block. Flagged-tip bristles are resistant to acids and detergents. Polystyrene Bristles designed to hold water and cleaning solution while safely washing away dirt and grime from any surface on your car.