Featuring crystal clear lids and a 360° rubber gasket, these fly boxes are thin, light-weight, and fit comfortably in your vest or pocket. The patent pending IFF (Interlocking Friction Foam™) and adjustable divider compartments provide unique fly storage flexibility. The Crystal Creek Fly Boxes are available in 2 sizes with 6 customized configurations. Out of the 6 boxes 5 of them use the IFF (Interlocking Friction Foam™) Technology which features rows of interlocking foam that securely holds flies between the foam rows using friction without allowing the hook to pierce the foam.