The Hitech 77mm Circular Polarizer is designed to be used with the Hitech 67mm holders which have the optional accessory ring attached. Polarizers remove reflections from non metallic surfaces such as water or glass and also increase saturation. Rotating the polarizer crates the optimum effect for the conditions. NOTE: If you have an autofocus SLR or DSLR or other camera which uses a CMOS chip, you will need a circular polarizer rather than linear. The circular polarizer may also be used with other cameras suitable for linear polarizers. Hitech polarizers are made using the highest quality Schott optical glass.