I've used that and I regret it (this was way before I had any clue about what I was doing). In the heat, it is IMPOSSIBLE to use correctly. And the darn thing says not to use in sunlight or else it will activate it. Well, that was the only place I can use it, and boy was it a problem since it immediately activated. Basically, it turned hard right away, and there is no chance to fix anything at that point. Plus, it activates when it's still on the pen, so you can't use it since it dries out all around the tip, which prevents the stuff from coming out. It deserves some sort of award for worst product design of all time.
I bought it as a recommendation from some guy who worked at Autozone. I guess he never hears the negative feedback, because after experiences like that you'd probably never go back.