The sides and bottom of the coasters are made of cork so don't worry about your tables getting scratched. The cork also adds an extra layer of water protection. Most of the water should absorb right into the concrete, but the cork is there to save the day to catch any extra moisture. Because of the texture of concrete, no need to worry about your glass sticking to the coaster. No suction cup action happening here!
Set of 4.
Dimensions: 4" l x 4" w x 0.5" h.