I received this for evaluation and thought that I would give it a try with a Fujifilm X-T3 mirrorless.

Generally, I run a UV filter on my lenses for a bit more protection from the elements (I like to shoot at the beach a lot and the salt air can easily leave a coating on the lens). But when I want to achieve slower shutter speeds to soften waves, I utilize a series of ND filters. This requires me to add a filter holder in front of the lens and then slide my ND filter of choice into the filter holder.

This set up makes the whole process so much easier. I can attach the included magnetic holder into my 18-55mm zoom lens. Then, when I want to attach the variable ND filter, I reach into my bag, pull this baby out and let the magnet attach it to the lens. It spins freely so that I can dial in the amount of ND that I want. No more fussing with multiple filters stacked in a filter holder. That makes me happy and leaves less room for error, more space in my camera bag, and less fumbling at the beach with the wind and sand blowing.

It is a tad pricey to me but the overall improvement of time, effort, and ease of use make up for the price.