The COKIN CREATIVE SYSTEM consists of 3 main components: An Adaptor Ring A Filter Holder 1 or more filters. The COKIN Filter-holder can be precisely adjusted and attached to the lens by means of a screw-in adaptor ring. A change of camera or of lens necessitates only a change of adaptor ring, not the Filter-holder nor the filters. The COKIN Filter-holder has four grooves. One holds round filters, which can be rotated in the groove. The three others hold square filters which can be adjusted up or down at will. The Cokin Advantages Same filter for all your lenses by just replacing the adaptor ring. Rotate, slide, decentre in all directions for more precision and creativity Wide Range of Filters The COKIN A & P Series include a complete range of over 180 filters for a maximum potential of creativity, while the Z-PRO & X-PRO Series contains over 90 filters among the most used by professionals. The Cokin Sytem is available in 4 Series A Series : Comprises a complete range of COKIN filters for lenses with diameters up to 62mm. A wide range of adaptor rings as well as numerous dedicated accessories (Holder Cap, Ring Cap, Coupling Ring, Modular Hood, Modular Bellows, Wallet & Storage Boxes,etc.). The "A Series" is recommended for focal lengths 35mm onwards (35mm format). Filters are 67mm wide. P Series : For larger diameter lenses up to 82mm. Recommended for focal lengths from 28m