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