Our Sophia Logo Coasters are 3.5" round and cut from thick solid-core birch wood, hand-sanded, stained, and affixed with a cork bottom to keep the coaster from slipping. The wood is selected to be naturally heavy and resist warping, and the stain protects the appearance of the coaster. They are unsealed to preserve a natural surface and allow absorbency, and the Sophia Coffee logo is carved directly into the surface for a beautiful finish.