Orbit Plastic Sprinkler Guard Donut. It prevents grass from growing over your sprinkler heads, ensuring optimal spray patterns. Made of durable plastic, this guard can withstand extreme temperatures and impact. Molded in a solid green color, it blends seamlessly with your lawn. It fits spring loaded pop-ups, gravity pop-ups, and fixed pattern sprinklers of all manufacturers. The diameter of the center hole is 1.8".