They look VERY cool and the Yellow and Green glow particularly well under a Black Light. I find they are better coasters for larger, heaver items like wide and liquor bottles. They have a non-slip backing so they stay in place on the table.
These are a great addition to a handout room. We changed one of our lightbulbs in our overhead light in our living room to a black light, so now we get to enjoys these coasters glowing while we eat dinner and play video games after work.
These add a crazy cool factor to our Halloween party setup too.