Haven't seen these before, but soon will. Just ordered some off eBay. Thanks for sticking them on.
I've used them before they are ok, but what I don't like about them is when you crimp them like any other crimp they crimp across the line and I think if you crimp it to hard you can weaken the line. So I've been using this tool and the crimps and rubber inserts that are made for this crimping tool from breakaway, I like this idea, I know I can use silicon sliders but they can move a bit too much.
Crimp Tool