The grooves on the front end of {TAIL ~ device} face proximally and are disposed on opposite sides of the device in {HEAD ~ alternating fashion} 
The grooves on the front end of { TAIL ~ device } face proximally and are disposed on opposite sides of the device in { HEAD ~ alternating fashion }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD