Orbea R10 El Manual Del Propietario página 9

Fig.5
If your helmet came with a locking buckle, you will need
to flip the lock up, adjust the strap then lock the strap in
place by closing the lock. (Figure 6)
If your helmet came with a push button buckle, adjust
the straps then insert the clip to fasten.
Push the button to release. (Figure 7)
Fig.6 Fig.7