It does work on all barrel locks (allegedly) if you have the right diameter and softness of pen. The plastic deforms as you push it into the barrel and with a twist of the wrist the pins find their own keying, to allow the lock to open.
Beware that it f**ks your lock up as I've not been able to reset the lock using the same method, without filing down the tab on the key and doing it that way!
I find that my daughter's Crayola Colouring felt-tip lids are the best ones, but once the plastic starts to wear you need to trim it down with a knife or pair of scissors to make it work again.
I'll try to remember to bring my demo lock and pens along to Cadwell and will teach you how to do it...