The Key Defender is a neat little gizmo, but best reserved for people who are physically fit and have some hand-to-hand skills. It's a tiny spay vial with three-ish shots of a fairly short range cone-type spray.
The range problem is common to the smallest form factors of OC spray, like the little keychain size unit in the picture below. It can be mitigated some by going with a stream instead of a spray, but then you have to aim better to walk it across the eyes. Get an inert trainer and take some test shots so you have an idea of how far the thing will shoot and what the pattern looks like.
