Flexible Roane Tip Stainless Steel File. The Flex-R file is the most popular Union Broach endodontic hand file it is desighed with the patented "R" tip - superior triangular K-type flute design developed by Dr. James Roane. A patented computer-controlled manufacturing process ensure consistency in size, flexibility and strength. These features give the Flex-R file greater capabilities to follow along the curve of the canal, to ensure the most comprehensive cleaning and shaping procedure.