{TAIL ~ Outer tube} 102 is provided at its distal end with a window 120 having a peripheral edge 122 entirely surrounded by {HEAD ~ an angled land surface} 124 
{ TAIL ~ Outer tube } 102 is provided at its distal end with a window 120 having a peripheral edge 122 entirely surrounded by { HEAD ~ an angled land surface } 124
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH