Sena X1S User Manual page 10

1 ABOUT THE X1S SMART CYCLING HELMET
4. After removing the chinstrap pad, adjust the chinstrap tension at
the buckle with the strap adjuster in the proper position. Adjust
the tension so the chinstrap is tight and comfortable by pulling the
chinstrap end through the buckle to either tighten or loosen as
needed.
5. Secure the excess strap with O-ring and then attach the chinstrap
pad. Always wear the helmet with the chinstrap buckle fastened and
the chinstrap pulled tight and positioned back against the throat.
With the strap buckled and the helmet positioned, you should feel
the chinstrap pull firmly against your chin as you open your mouth.
When properly adjusted the helmet will wrap around your head and
cradle it with firm, but comfortable pressure.
Chinstrap Pad Chinstrap
Sena X1S Smart Cycling Helmet | 10
O-Ring