Gray filter with Helix MagLock Filter System. Gray filter with a diameter of 101 mm. Helix MagLock magnetic attachment system. Optical glass with multi-coating. Front and rear defender caps. Filter ring made of brass. Rubber frame insert provides more grip. The Helix MagLock filter system is designed to eliminate the hassle of screwing on and off filters while providing a filter that securely locks in place after installation. Unlike other magnetic filter systems on the market, Helix offers an absolutely secure connection through the quarter-turn magnetic locking mechanism, allowing for quick attachment and removal of filters while ensuring they stay in position even in the most demanding shooting situations. These filters won't go anywhere until you take them off your lens. With available brass thread bases of 67mm, 72mm, 77mm, and 82mm, Helix easily covers your entire lens arsenal. 1x ND8 filter, 1x front, 1x rear defender. ND filters extend exposure time. A neutral density filter (ND filter), or gray filter, blocks a portion of incoming light. With a gray filter, you significantly extend the exposure time, achieving effects such as blurred water or preventing overexposure in bright sunlight with an open aperture.