The ULS does not come into contact with the front glass unless intentionally pressed to touch the glass or is taking a blow from dropping the lens. Dirt, by default, does not come with your packaged ULS. If dirt, fine sand or debris enters in the inside of the ULS, there is no need to worry. We’ve already infused a special coating into the material of the ULS, making it so any collected finely grained silent killers (dirt, sand, debris, etc.) can be washed off and dried, looking brand new, within seconds.