Electra Reflective CE Helmet in Grey

retention system provides a secure and snug fit. easy-to-use magnetic fidlock buckle. size small fits circumference 48 cm - 54 cm and hat sizes 6 1/2 - 6 3/4. size medium fits circumference 55 cm - 58 cm and hat sizes 6 7/8 - 7 1/4. size large fits circumference 59cm - 61cm and 7 3/8 - 7 5/8. small size generally fits children while medium and large sizes fit adults.