Scorpion Helmets A small metal tape measure or a cloth tape may be used to make your initial measurement. You can also use a string, which can then be laid against a measuring tape. Measure the circumference of the head at a point approximately one inch above the eyebrows in front, and at a point in the back of the head that results in the largest possible measurement. Take several measurements. The largest measurement is the one you want to use. Scorpion Snow Helmets tend to fit tighter than the sizing chart may suggest. If you are in the middle to upper range of a size please consider going up to the next larger size.