The filters in this set are custom fitting for the Mini Pro 5 drone lens, and this range comprises five filters which are combined neutral density/polarising filter and one standard circular polariser.The ND/PL ones are ND4, ND8, ND16, ND32 and ND64 and the CPL is a straightforward polariser. The front of each filter has a very lightly grooved rotating ring stiff enough to avoid rotating during flight and will need to be set before flight to the required polarising/density requirements. A tiny white mark around the outer edge of the ring and a small white mark on the filter body act to serve how much the filter has been rotated.The filters weigh less than a gram so ‘should’ keep the drone below the all-important 250g take-off weight, and the filters clip firmly onto the front of the drone lens so shouldn’t come loose during flight. It’s useful too that filters can be left in place and the lens protector strap fitted over it when the drone is packed down and transported.The filters work well in practice, most useful for me is the polarising effect for reducing reflections – it took me a little bit of experimenting to find the best rotation position but the white calibrations help to retain the best setting for subsequent flights.The filter set comes supplied in a flip top case with foam insets to keep the filers safe. I found removing them from the foam slots very fiddly but if they are reinserted at 90 degrees from the original position they are much easier to remove and replace (see photos for the two positions).