This Conversion is designed for fly tying on tubes which are strung onto a leader normally with a small short shanked hook. Very effective patterns especially for large aggressive game fish can be created which also cast quite well. The Nor-Vise Tube Fly Conversion comes with four mandrels, matching collars and will accommodate a wide range of tube materials, sizes and types. The tubes can be rotated, spun and locked on perfect rotational centerline and will not slip, turn or move.