Swirl marks are caused by bits of dirt and dust rubbed across the car's paintwork during washing The Grit Guard helps prevent this. The Grit Guard can simply be placed at the bottom of the bucket. Every time you run your wash mitt through the bucket for more suds, you also rub it against the Grit Guard. This helps remove the dirt and, in addition, the Grit Guard ensures that the dirt stays at the bottom of the bucket. Comes with a yellow bucket of about 13.5 L in which the Grit Guard fits exactly.