Helmet attachment

STRAP

It keeps your headgear securely in place when fastened under your chin.

A helmet attachment is something that secures the helmet to your head, and the most common term for that is a "strap." The word is straightforward here—no hidden wordplay or tricks—just a direct reference to the adjustable band that fastens under your chin. If you’ve ever worn a bike helmet or sports gear, you’ve used one of these to keep it in place.