and the flexible distal portion 902 of the flexible endoscope liner 900 in contrast to the annular or helical convolutions of the previously described embodiments the present embodiment has a helically threaded flexible distal portion 902 the helically threaded flexible distal portion 902 has an external reinforcing thread 912 that traces a helical path around the distal wall 908 of the flexible endoscope liner 900 a land 914 having a reduced wall thickness traces a helical path around the distal wall 908 separating adjacent turns of the reinforcing thread 912 the width of the lands 914 is typically 100 150 percent of the width of the external reinforcing thread 912 typically the thickness of the distal wall 908 at the lands 914 is approximately 60 80 percent of the total wall thickness measured at the peaks of the external reinforcing thread 912 the external reinforcing thread 912 may be made as a single helix as shown in fig9 a or as a double triple or multiple helix the external reinforcing thread 912 may be made with a semicircular profile as shown in fig9 c or it may be made with a rectangular triangular trapezoidal or semi elliptical profile or other desired profile in a particularly preferred.