Here is a Stan’s NoTubes Core Remover Tool† holding a Presta valve core. A few weeks ago when preparing to ride Poto the nut came off the top of a valve core, and today I finally got around to replacing the core with a spare. There was something that I liked about the look of the core in the tool, and normally one doesn’t see this side of the valve, so here is a photo of it.
† I own both the Stan’s Core Remover Tool and the Park Tool VC-1 Valve Core Tool and, in my opinion, the Stan’s tool is much better. For some reason the Park VC-1 doesn’t fit on a number of the Presta valves that I have, whereas the Stan’s fits on them all.