These coasters range fro 3.5" to 4 " diameter. Sustainably harvested from our savannas of Oregon white oak that have retired to the ground. The rings on this coaster are extremely tight, and you will notice that these oaks have been on this earth long before us. We carefully remove the soft outer bark, and leave the cambium layer. Then we finely sand the top side to a smooth finish. We leave the bottom so the coaster has good grip on the table. Then we steep these coasters in a special mixture of our own beeswax and essential oils. These trees provide excellent wildlife habitat, and we only cut these oaks as part of a forest restoration project.