Pro Sportfisher Flexitube is a revolution within modern tube design! An industry 1st and Pro original, Flexitube is an injection molded tube design where the tube is made in two dimensions but in one piece! What does 40/40 mean? The front half or tying surface is 40 millimeters long(about an inch and a half). The back half works as an integrated hookguide which is also 40 millimeters long (about and inch and a half) and is the basic makeup of Pro Flexitube 40/40. Although there is a designed tying surface/integrated hookguide surface, tyer's use these dimensions in many ways. Some will tie strictly and only on the tying surface and trim the integrated hookguide to the desired length. Some tyers will start the fly near the end of the integrated hookguide for the back end of the fly and body while adding weight or a cone and finishing the front bit of the fly on the smaller 40/40 tying surface. Others will start near the back end of the integrated hookguide and use nearly the entire tube in creating large and unruly predator flies.