These weighted sleeves integrate with both the Pro Sportfisher Flexitube and Pro Sportfisher Microtube systems. A Flexiweight can be added to a fly near the front middle or rear of the tying tube to change how the fly will ride in the water. Other tying materials can be added behind, in front of, or over the top of these tubes for many effects. Flexi Tubes are very finely finished, and very easy to use. They help add weight to your fly without adding bulk.