Avoiding swirl marks is one of the biggest challenges with today's delicate clear coat finishes. Grit Guard helps prevent the formation of swirl marks during vehicle washing, which can be caused by sand and small dirt particles. Each time you dip your wash mitt into the wash solution, you wipe it against the Grit Guard bucket insert, which removes dirt particles from the wash mitt and deposits them at the bottom of the bucket. The specially shaped fins of the Grit Guard prevent the swirling and re-absorption of dirt particles.