Mug coaster - caffeine molecule

This coffee coaster is wide enough to fit most mugs. The indented symbol is the molecular structure of caffeine. I added a groove on the bottom for an o-ring (the groove is sort a dovetail groove slightly modified to help it print well). Since just a pure plastic coaster would likely slide on my desk surface, I added the o-ring to help keep it in place - and it works pretty well!