This four-pack of K&F Concept Go Ultra filters has three neutral density filters and one circular polarising filter. To use them, you need to unscrew the protective glass that is already on the camera which can be on quite tightly, then just screw on the one you want.One thing to note is that the original lens protector has a convex surface and as a result of that, the glass can be a lot smaller. These four filters, however, are made from flat glass and so as not to get vignetting they are a lot larger - 23mm for the curved glass and 31mm for these flat filters.The three neutral density filters are three, four and five stops which should darken down the sort of illumination levels that you will experience in snow or bright sunlight.The polarising filter only has the edge of the rotating portion on the front so you can screw that in in the same way as the other filters. There is a small white mark on the edge that lets you know the orientation of the polarisation so that you can set it up quickly.The polariser in this case is circular polarising as opposed to linear polarising and you can get into trouble with that where you wouldn't with a linear polarising filter - with it being quite a wide angle, with a circular polariser, you can end up with a dark band where a lot of polarised light is absorbed but lighter bands on either side where less is absorbed, making the picture inconsistent. You will find that you get better performance from it if you select cropping modes that use less of the sensor thus eliminating any banding.This is a useful kit to keep with you if you need to reduce the amount of reflected light in your images or if the lighting conditions are too bright for the sensor.