A favorite with welders nationwide, the Big Window offers lightweight and nearly 24 square inches of viewing area. We've taken a standard 5 1/4" x 4 1/2" welding lens and placed it vertically to give you the best possible view. The Big Window helmet is made of tough, washable thermoplastic. It includes our "contour-comfort" headgear featuring double lock locking devices and our patented Zahnlok adjustment. Huntsman patented Zahnlok adjustment system allows the wearer to adjust the headgear in 1/16" increments to exact head size, simply by turning a knob. The adjustment is automatically locked in with 50 meshing teeth to ensure a snug, comfortable fit that wont slip. The system is durable and long lasting, because the teeth are automatically disengaged while the headgear is being adjusted.