These 4 inch drill brushes are uniquely designed for effectively cleaning car interiors and exteriors. The durable nylon bristles come in 3 different stiffness variations to powerfully yet gently clean everything from car upholstery, carpets, rubber mats, and even headliner. Other drill brushes are either too large or too small to easily fit into the endless cracks and crevices of a vehicle. If they are too small it takes too much time, and too large just creates too many opportunities for you to damage the area you are scrubbing. The 4 inch diameter design is a suitable size for cleaning every area effectively without putting you at risk of losing control and ripping through carpet or scratching a wheel. The nylon bristles are designed with 3 different levels of stiffness so that each area being cleaned has the appropriate brush behind it. The white bristle drill brush is the softest. This specific brush can be used on headliner or upholstery for effective and gentle scrubbing. The yellow brush is the medium stiffness designed for carpet, floor mats, and even to stir up pet hair, crumbs, and anything else that may not be able to be vacuumed. The red bristle drill brush is the stiffest and should be used on rubber floor mats, wheel wells, tire side walls, and anything else that is particularly resistant to scratching. Each brush was created with more bristles than the standard drill brush to increase cleaning power, durability, and simply to lower the amount of bristles that may fall out over time. This 3 piece set was made specifically for the auto detailer for cleaning cars in a safe and reliable way.