{HEAD ~ A flexible lubricous sheath} which covers at least a distal portion of the flexible coil of the instrument is provided with {TAIL ~ either contrasting colored stripes} or palpable ridges, or both, which are located a predetermined distance from the distal end of the instrument 
is provided with
{ HEAD ~ A flexible lubricous sheath } which covers at least a distal portion of the flexible coil of the instrument is provided with { TAIL ~ either contrasting colored stripes } or palpable ridges , or both , which are located a predetermined distance from the distal end of the instrument
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL 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 OTH