EST-FLO-TIP New old stock, blister carded Esterbrook Wonderiter Flo-Tip. This is a felt tip replacement for Esterbrook cartridge fill Wonderiter fountain pens. Think of it as a felt tip writing unit! I'm sure these are still usable if you have the right Esterbrook for them. Even without the pen, they're a neat little collectible Esterbrook item. (5 avail)