I have at least one in every color I have been able to find. I have used these for everything. They will write on everything I have tried. I even ended up using them in my daughter's baby book because it had shiny pages and everything else smeared. These are great pens. Everyone should have at least 3 or 4 in their stash.
Great pens, but I don't understand why a 3-pack would cost more per pen than buying them individually. On sale, a 3-pack is $7 ($2.30 each) and the individual pens are $1.75 each when not on sale. Maths.