When it comes to safe transportation, I try to take every preventive measures no matter how unlikely I will ever need it. First aid kits, flashlights, safety triangle, fire extinguisher, light reflecting outfit and finally this one, these make make up my doomsday inventory so far. Among them this may look to be the most extreme item but believe me people do get trapped in the car and unfortunately lose their lives just because they can not free themselves in time.I am afraid I don't have hands on experience about how this device works and I would never want such an experience, but just by writing the name resqme on youtube you will instantly see over 20 videos about that device. There you will see that it can really cut through the seat belt with one blow and somehow pulverize the window glass within seconds... So when you need it, if you can keep calm, it may take less than 30 second to get yourself out of the vehicle which would otherwise take minutes or not be possible at all.Due to great reviews and demonstrative videos, I purchased this item. I paid around $10 for a single one but sometimes there are bundles on amazon and you can buy a dual pack for $15.Although it is designed as key chain which is how you can keep it accessible on an operating car (provided that you don't have one of those new keyless devices) but like many other reviewers, I did not put it on my keychain. Although it is as small as it can be, still takes up some space in your keychain and feels bulky. Besides, since it has a built in blade, it may be misunderstood as a knife and put you some headache in airports and places like that. So, to me the best place to carry it is in the glovebox in a tiny case. But make sure that at no circumstance, it moves from where you put it and that you can access it easily from where you are trapped. This solution may not be ideal for some people and/or cars but then I advise you to look for a place that you can use for the purpose.I wholeheartedly recommend this product for anyone who values their life and wants to raise the safety level of their car trips and wish that you will never ever need to use it...