Thirstystone quarries their sandstone for the Coasters in the Southwestern United States using the most environmentally conscious methods to extract the sandstone boulders that will be crafted into Thirstystone coasters. Thirstystone Sandstone Coasters are among the finest in the world, due to their incredible absorbing ability. The unusual nature of the porous sandstone literally absorbs messy drips from beverages without leaking onto furniture. They also do not lose their ability to absorb over time. The Coasters come in a set of 4, with each one being 4" in diameter and 3/8" thick. Each has a cork back so as not to scratch surfaces.