no wider than your steerer tube and no longer than your fingers

This ensures the spokes are never getting extra stress put on them by rubbing on the flange

The 4" length is just about right for people that want to look like a mountain biker without looking like they've just stepped out of a Crossfit box

and a compression design provides enhanced muscle support

See the link at the bottom of the description

TLD Flowline SE MIPS Helmet - XL-2XL - Pinstripe Charcoal - Black PLP|EMTB Optimised no wider than your steererDETAILS Be sure to stay safe on your bike rides with the Flowline SE Helmet from Troy Lee Designs. This half shell helmet seamlessly combines safety, comfort and style. Enjoy reliable impact absorption and a breathable airflow system with the helmet's design. Plus, the easy to use magnetic buckle ensures a secure closure every time. Conquer the mountain bike trails, or city streets, with the Troy Lee Designs Flowline SE Helmet. SPECIFICATIONS 3 Way