Concrete Round Charcoal Coasters, Set of 4The Port Living Concrete Round Coasters offer the benefit of being both absorbent and relatively stain resistant due to the sealer used; yielding just the right porosity to the coasters. Backed with cork for tabletop protection. These tabletop coasters are hand burnished with FDA approved sealer using PLC concrete. Sustainability Portland limestone cement is a blended cement with a higher limestone content, which results in a product that works the