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. 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, adding virtually no weight.
Warning: Please remove the o-rings from the old cap and put on your new Bust a cap to insure that your light remains water tight.
WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov