The Cokin Small Magne-Fix ND 4x Filter gives photographers with unthreaded camera lenses a chance to achieve special effects and filtration that they don't ordinarily have a chance to do.
This system features a unique mounting technique where you peel off a protective film from the back of a mounting ring that contains an adhesive surface, which is then pressed against the edges of your lens. The reverse side of the mounting ring is magnetic. The filter is then held firmly against the magnet. When finished with the filter, grasp it firmly and remove it.
Neutral density filters let you adjust exposure without affecting color balance. They appear gray and reduce the amount of light reaching the film. The 2-stop value (ND 0.6) effectively compensates average situations.