This is the first distance of travel {HEAD ~ the temple} may flex beyond {TAIL ~ its fully open, unbiased position} on the eyewear 
This is the first distance of travel { HEAD ~ the temple } may flex beyond { TAIL ~ its fully open , unbiased position } on the eyewear
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH