This is a cooking tray, but may also be known as a turntable tray, and it is used in conjunction with your microwave or oven/microwave combo. The outer diameter of this part is roughly 12.75 inches. The tray is made entirely of glass and is colorless. The purpose of this part is to act as a stable and even cooking surface for your food to...Read more sit on during a cooking cycle. To ensure a more even cooking temperature the tray will also spin when your appliance is activated. The most common reason for needing to replace this part is if your current one has been damaged.