I wanted a place to stash an emergency key for my house and couldn't find anything commercially available that wasn't overly large or so common that it was obvious. I suppose this could be used in place of a Hide-A-Key for your vehicle, but this was intended for a static object and I would strongly encourage testing before trusting this to the stresses of speed and vibration that are common to driving around.

Printed in 95A TPU with four 6mmx3mm magnets. Pause at ~5mm Z to insert the magnets before continuing the print.