Most people with an interest in photography will immediately recognize the K&F Concept name as a maker of quality photographic gear, and these GoPro lens filters are no different. High quality multi-coated optics are used in both the CPL and ND filters. With this lens set, you get three ND filters (ND stands for Neutral Density — more on that in a minute) and a circular polarizing filter. The CPL filter is a circular polarizing lens filter. These are used to reduce glare in your videos and photos. It also helps bring out the deep blue of the sky when shooting the sky, clouds, etc. You can rotate the front of the CPL lens, which is a great feature as it lets you see in real time what effect it is having on your color as you rotate it. The ND or neutral density filters basically act as "sunglasses" for your camera's lens and sensor. They're available in 8, 16, and 32 level reductions, giving you plenty of variety and choice. A fairly typical use of an ND filter would be photographing a waterfall. You want the classic image of a static landscape BUT with the water showing movement and flow. In order to achieve this, one would have to deliberately overexpose the shot to give the water movement. However, in doing so, everything else in the image (except for the waterfall) is blown out and overexposed until it's almost entirely white! Now when you put an ND filter on the lens, you force the shutter to stay open longer, resulting in a perfectly exposed image with the flowing water in the waterfall. This is a great lens set to have in your GoPro gear bag. One person found this information helpful