Just received an Esterbrook cartridge pen (without cartridge ). I'd checked its photos on eBay and it looked as if the nib was missing; just the feed left screwed into the section. Still, the price was good and I have spare nibs so I bagged it. What I received was the pen with a used fibre tip 'nib' which screws into the section just like any other Estie nib. I have an unused tip of this kind in a box which told me it's a Wonderiter [sic - sorry for error in title] flo-tip. I'm soaking the old ink out of the tip at the moment and had an initial writing test with the revived dried stuff, and it had that scratchy feeling of any felt tip. I've done a quick search on FPN but haven't found anything about the flo-tip. I wonder whether anyone has actually used one of these tips properly inked, and what their experiences were. Any thoughts on the history of the thing would also be gratefully received.