If the assembly is correct, the strap's free part must be accessible with the mask in order to easily adjust the head harness.

1. Start the installation with the middle, upper strap in the head harness, 97843-951. Thread through the strap, with the direction from inside the mask. The IS mark in the middle of the head harness must be visible after assembly. Thread through the strap's end in the mask buckle's yoke and back above the yoke.

1. Fold the strap and thread back on the other side of the buckle's yoke.
2. Thread in the two upper side buckles and finally the two lower side buckles.