If you carry a full size flashlight, like the Streamlight 20 XP LED or the Streamlight 20 XP Poly, the cap alone will not break glass (see our videos). This flashlight is made out of a Polymer case, which as you know, feels like plastic. There is no way you can break a window with this flashlight.  Attaching Bust A Cap® to your flashlight will insure that it will break glass with a simple “tap,” virtually adding no weight.