Universal Medium-Large Size: This helmet caters to a wide range of users with head circumferences ranging from 20.0 inches to23.75 inches. Extra Large: Head circumference 22″-24.4”. Lightweight Design: Weighing in at less than 3.7 pounds, this helmet won’t weigh you down during extended wear. Versatile Compatibility: Designed to accommodate communication systems, gas masks, and helmet-mounted night vision goggles, our helmet offers seamless integration with your essential gear. Fully Adjustable Harness: Achieve a secure and comfortable fit with our easy-to-adjust harness, ensuring your helmet stays in place when you need it most.