I recently bought one of these pens, and they're cool but I have a huge problem with them...apparently I draw my lines TOO FAST because they erase themselves as I draw them. I guess the friction of the ball moving over the fabric heats it up enough to erase the ink!! I end up with a really pale line, about as dark as a pencil mark. I have to really slooooow down to get a dark line and that drives me nuts so I've switched back to my faithful mark-b-gone pen. Probably can use the frixion pen for something like drawing applique shapes where I'd be going a lot slower. But for marking straight cut lines, I'm just too speedy for it!