To ensure proper measurements we recommend the use of a soft measuring tape or a piece of non stretch string or yarn. Take a measurement of the circumference of the head 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, to make sure you have the largest one. This chart was designed as a reference only. Actual head shape is an equally important factor when determining the best overall fit.