Mahjong Joker Drink Coasters, Mah-Jongg Table Game, Tournament with Friends 3-D Printed These coasters would be a wonderful addition to your weekly game play or tournament. Fun birthday, Christmas or a welcome to the group gift. Each coaster measures approximately 4" x 4" with a cork backing. Coasters are made of PLA plastic. Not dishwasher safe. Hand wash with soap and warm water.