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