4916FM CC FLY BOXL-RM FOAM/MAGNET Crystal Fly Boxes feature clear lids and a 360 degree rubber gasket, these fly boxes are thin, lightweight and fit comfortably in your vest or pocket. The patent pending Interlocking Friction Foam (IFF) and strong magnet in the base provide quick easy access to nymphs and smaller flies. These fly boxes are a great way to organize a day's trip on the water.