Flexible tubing

Flexible tubing comprising contiguous, tubular wall portions of melt-extrudable materials including one set of a plurality of wall sections and a second set of a plurality of wall sections in which each wall section of said one set is contiguous with a wall section of said second set, said wall sections of said one set being constructed of relatively stiff resilient material and being uniformly distributed along said tubing, and said wall sections of said second set being constructed of flexible material, each said wall section of said second set having a length no greater than twice the diameter of said tubing, and wherein certain of said wall sections of said one set differ perceptibly from the remainder of said wall sections and are located along said tubing separated from each other by a predetermined number of said remainder.