This kit contains the following 4 x 5.65" filters: Tiffen Circular Polariser, Clear, Warm UV-17, and Soft Pouch. Circular Polarisers Reflected light rays become polarised. Polarising filters are used to select which light rays enter your camera lens. They can eliminate unwanted reflections from non-metallic surfaces such as water or glass and also saturate colours, providing better contrast. The effect can be seen through the viewfinder and adjusted by rotating the filter. The filter factor varies depending on the rotation of the filter and orientation to the sun. The filter factor varies between 2.3 and 2.8 (approximately +1.3 stops). Circular polarisers are specifically designed for use with autofocus SLR cameras (they will also work perfectly on manual systems and video cameras). Clear Filters A clear (colourless) filter for colour and black and white films. Also serves as permanent protection for the lens. Warm UV-17 Filter Haze (UV) filters are wise initial investments. They help protect your valuable investment from dust, moisture and scratches, which can lead to costly repairs. If desired, they can be left permanently on the lens for constant protection. Haze filters provide additional correction benefits for ultraviolet (UV) light which can register on film and videotape as a bluish cast and can obscure distant details. Ultraviolet filters allow you to correct the UV effect to varying degrees. UV-17 filters absorb approximately 97 per cent of UV rays.