The adjustable strap 308 in the rear is used to adjust the headset to {HEAD ~ a comfortable tension} setting for {TAIL ~ many different head sizes} 
setting for
The adjustable strap 308 in the rear is used to adjust the headset to { HEAD ~ a comfortable tension } setting for { TAIL ~ many different head sizes }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL