The elbow 1, wherein {HEAD ~ the arc} of {TAIL ~ each channel section} extends through approximately 90° 
of
The elbow 1 , wherein { HEAD ~ the arc } of { TAIL ~ each channel section } extends through approximately 90 °
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH