The specialized sierra womens commuter helmet offers serious protection and is full of clever features to make it exceptional value for money the helmet has a one size system which has been based on womenrsquos head sizing so you donrsquot need to spend time measuring your head the one size hairport sx system perfectly accommodates a ponytail and features a micro adjustable dial for a perfect fit you can also easily adjust the straps on this helmet thanks to the tri fix web splitter