I like hexagons. Yes really, check out some of my other designs. Anyway, wife was annoying me with "you need to use a coaster to avoid water stains on the wood", but our collection of coasters was a jumbled mess and most of them wobbled.

So, I made these. A vaguely Aperture Science inspired design, stackable, with a nice holder that takes 12 coasters. The example picture is printed in Prusa OhMyGold PLA, the holder in Galaxy Black PLA (my favorite).