Put more simply, the ND filter helps avoid overexposed photos.
The ND4 filter allows 1/4 of incoming light through, equal to a 2-stop filter.
The ND8 filter allows 1/8 of incoming light through, equal to a 3-stop filter.
The ND16 filter allows 1/16 of incoming light through, equal to a 4-stop filter.
The cover of the lens is great. I used it in a combination with the little foam gimbal lock.and the gimbal was well protected. Ordered it from this store. I like the level of their services. They offered the lowest price.