The Lazer O2 is ready when you are, whether it's a commute, sportive or you're attaching anaeroshelland sprinting for the win, the O2 helmet is ready for it. The O2 is a compact profile helmet which is lightweight, well vented & a great fit with all the features of a helmet twice its price with added reflective panels for rear visibility. Rollsys is Lazer's very own award winning fit system: simply control the size & the comfort by turning the wheel on the top of the helmet which will adjust the fit of the helmet symmetrically without any pressure points on the head all with a simple one-handed adjustment.