A 5" Standard Clamp with a Medium (5 mm) ID tube best for fly sizes #16-#22, or a 5.5" Standard Clamp with a large (8mm) ID tube best for fly sizes #8-#18. Designed for easy hands-free release of fish. Simply slide the tube down your tippet until the fly is inside the tube. A quick pop or jiggle and the fly is free from the fish. One big advantage of this set up is when a fly is twisted or obstructed from the tube, you can simply use the clamps in the traditional way to remove the hook. Can easily handle all streamside tasks. Best to match the size and type of flies you use to the release tube size.