Zombies Rubber Square Coaster set (4 pack) Great Gift Idea by MYDply. $4.95. This 4 pack of 3.75" x 3.75" square rubber coasters of the image shown are made of a durable heat-resistant polyester fabric top, backed with a neoprene rubber non-slip backing, keeps things from sliding. The rubber coasters are 1/8" thick. It will not discolor or fade, machine washable.