The DuoLock twist-to-lock system is compatible with all Optiline holders. The ring made up of 34 magnets makes mounting your phone faster to the MAG series of mounts and accessories. Place your phone close to the holder and the magnets will do the rest. Edge-to-edge coverage and reinforced corners to increase impact resistance. Safety strap included. Perfect compatibility with all MAG phone holders/accessories and Duolock attachments.