I got these Ultra-fine tips a few days ago and have only just got round to doing more than a quick doodle with them. Colouring small areas and adding fine detail is so much easier now!
Basically, the tip just clicks on the fine end of your Promarkers and then after a little scribble on some scrap paper, the ink flows as normal. They can be cleaned so you don't need one for each pen you have. I've got three of these and it seems to work fine. I've even found that if you're just changing to a different shade or a similar colour then as long as you scribble a little bit before applying to your image the colour turns out fine.
They come with their own lid so you can leave them attached to your pen if you wish and they're even fine enough to write with.
