Sparco RF-5W Martini Racing Helmet - Size M+ (58-59)Sparco offer a wide range of helmets for both trackdays and competition use that benefit from over 40 years of experience in research and development. They study mainly in improving the aerodynamics and the material (weight reduction) of their helmets. How do I correctly choose the size of my helmet? Take the measurement of your head circumference above the eyebrows using a measuring tape: this measurement is usually between 53 and 64 cm with an