Pro-Tec Helmet Size Chart Circumference (Inches) Helmet Size: Small-20 7/8 Medium-21 5/8 Large-22 3/8 X-large-23 1/2. Measuring Your Head: To determine the circumference of your head, wrap a string or soft measuring tape around your head, just above your ears and just above your eyebrows. Putting Your Helmet On: To put your helmet on your head, align the front rim with the top of your eyebrows. Hold the straps on both sides and roll the helmet over the back of your head. Check for gaps. Pads should be flush against your cheeks and forehead. The back of the helmet should not touch the nape of your neck. With the chin strap fastened, your helmet should be snug and comfortable. Try to roll your helmet off your head. If the skin on your forehead moves, you have a good fit. Be sure your helmet is above your eyebrows and that your goggles fit your face while wearing the helmet.
