I always bothered by drip on the glass of cold drink.
It makes table wet and stick with the coaster.
It's common but troublesome problem.
Ordinary coaster, condense itself after a while.
One made by cork, get wet and does not dry easily ,so unsanitary.
Latticed inner saucer never stick with glass.
Extra large outer saucer has also large heat capacity, withstand cold dew from glass for hours.
Please view youtube movie below.