Thank you! Here's the "Round Object Sander". I just checked and they're called, "Flex-i-File". Here's the link to the page on their website.
https://www.flex-i-file.com/flex-i-file.php
It comes in a set of three frames and three different grit sanding bands. MicroMark sells them. They conform around the shape so you don't sand any flats into the surface. They're great for sanding joints on aircraft models, especially ordinance. The grit fills up pretty quickly so I use them wet by occasionally dipping it into a vat of water.
It's one of those tools that you buy not sure if you're going to use it, but then find that it comes in real handy for special things. I've got a raft of these kind of gadgets.
