This part is the oven bulb lens cover. It is made of glass and is approximately 3 inches in diameter. The lens cover protects the light bulb from being damaged. The main reason to replace the light lens cover is if it is cracked, damaged, or missing. Be sure that the lens cover is cool to the touch before you begin this repair. To remove the lens cover, simply turn it counter clockwise until you can remove it. Replace it with a new cover and turn it clockwise to lock it into place. This is an OEM part sourced from the manufacturer, and it is sold individually.