UPDATE (AUG-21-2015): Scaled up to 80mm diameter. Have you ever put your glass on a coaster, and after a while when you try to take your glass again you also take the coaster with it? I hate that. So I designed my own coaster only thinking in how can I quickly drain the liquid off the base, so it can't do the 'sucker' effect on the coaster. This way liquid is drained to the external recess of the coaster and then retained there. Draining is optimised for low viscosity liquids, so don't expect it to work good on honey or ice cream. I opted here for cylindrical fluting, because it has better touch feel than other shapes like for example prisms, so its more comfortable to wash. I repeat I didn't think in its beauty, just funcionality. I don't think this thing is perfect, I call it 'perfect' as a joke, because maybe that is just convenient for my personal daily use. Happy drinking with Perfster!! Next I'll design the perfect cup!!!! :-)