The specialized chamonix commuter helmet is a one size helmet designed to fit a wide range of head sizes thanks to the headset sx fit system the micro adjustable dial ensures a secure and accurate fit and it39s extremely easy to adjust so you can have the perfect fit without any discomforts the chamonix helmet features specialized39s 4th dimension cooling system which optimises the ventilation to prevent your head from overheating the tri fix web splitter improves the ease of strap adju