The number one rule with any self-defense weapon - if it's not ready to use the second you need it, there's no point in having it.
This section lists products that are designed to be carried on your key chain, and therefore more than likely in your hand the whole time you are most vulnerable.
PLEASE, don't be caught out because you bought something but left it in the glovebox or in a kitchen drawer. By all means, carry a larger weapon as well, but always keep one of these handy versions at your fingertips.