This set of 4 coasters are created on hard-core art board, with alcohol ink. The ink is sealed, then coated with resin. This resin is heat resistant up to 500 degrees, so is safe for both cold drinks and hot ones. Each coaster also has a cork backing, to keep your home surfaces safe & dry. Coasters measure 4″ each, hex shape. The blue, green and gold alcohol inks will add colour and shine to your decor.