This bonnet fits our 20" green eco-friendly auto scrubber. It spins at 600 RPM to help conserve water and chemical, yet still offer the same cleaning capabilities. With this system, you can continuous scrub without having to stop and refill/dump your auto scrubber. This bonnet helps to create a truly "Green" cleaning system that creates less waste. This bonnet comes packaged as a single unit, and can be used on both sides. Once it becomes heavily soiled, we recommend rinsing out and then washing in our microfiber washing machine.