So I didn't know much about these when I got them, after trying them out with an adapter these definitely work great on Rusto cans. The only issue is that they don't seem to work on Spanish Montana hardcore. It sprays and then locks up, and doesn't work again.
Beyond that its always great customer service and delivery.
These are really great traveling pads for painting or drawing. I've been using them for years to paint small things at coffee shops. They even make a kind that's blank on the front and a postcard on the back.