The K&F CONCEPT ND8&PL + ND16&PL + ND32&PL+ ND64&PL Filter Kit arrives in a plastic carry case with a foam inner that has been sculpted to accommodate the 4 filters - they are arranged in increasing strength from top left to bottom right.The filters are multi-coated with the final layer being quite resistant to picking up fingerprints as well as beading water drops for easy removal using the provided cleaning cloth. They are lighter (6.3g) than the standard lens protector (10g) with a thinner surround, the very front ring rotates the Circular Polariser, the inner ring is used to screw / unscrew the filter from the camera.If you have not removed the lens protector previously, it may be rather stiff to unscrew...With the protector removed, fitting the chosen filter is simply a matter of screwing it in to the lens surround. The fit is very positive and should be as moisture resistant as the original protector as the internal design mimics that of the original. Removing or changing the filter is as simple as unscrewing and swapping filter, or replacing the lens protector.ND filters are usually used to reduce the amount of light reaching the sensor under bright conditions (or for creating cinematic effect), in order to get best utility from the filter set, setting the Action 6 to "Pro" will permit changing the ISO range used by the camera, as well as setting shutter speed ranges. Limiting the ISO to the lowest practical will make the best of the filters intended function, permitting control of light onto the sensor. The DJI MIMO app (which I dislike immensely!) does serve a useful purpose to monitor the settings the camera is using.The filters, in use, are as simple as it gets - the CP function can be used to reduce reflections from shiny surfaces (water is the most common use) as well as improve saturation of colours - a handy rule for sunlit scenes and a CP is that if the sun is shining onlto one ear, the direction the camera is facing is in the ideal (90 degrees) direction from the sun for maximum utility. Be aware that blue sky can be unevenly darkened when using the CP filter, which can look unnaturally dark over a portion of the sky, adjusting the CP slightly can reduce the effect.As far as value goes, 4 ND filters, each with a built-in CP filter for (currently) £44 is almost too cheap, given the quality of the product. (the 2 landscape photos below were taken without and with one of the filters, the CP filter enhancing the sky colour and reducing some reflections from the lake - the sun was shining on my left ear...)