The roller glide in your microwave rests under the microwave plate, and allows it to rotate when the microwave is running. It is a round plastic ring with 3 wheels spaced out around the perimeter. If your microwave plate or tray is not turning, you could have a broken or damaged rotating ring. This roller glide is made of white plastic and is approximately 11 inches in diameter. The 3 wheels are made of white plastic as well. This part is sold individually.