The Pro FlexiWeight system is a perfect way to add weight to your tube fly. All sizes fit over the 2,2mm outer diameter of the FlexiTube, NanoTube (even MicroTube) and of course the 2,2mm classic tube. All sizes are available in 4 colors which allows you to use as both weight and body in the "no-body" style of tube fly. The outer diameter of the FlexiWeight is 3,2mm, so if you slip one onto a FlexiTube, it fits perfectly with he thick part of the tube. This combination allows you use the thick part of the FlexiTube to hold your hook and if you want, the FlexiWeight can be hidden by tinsel or dubbing and integrated completely into the dressing of the fly. A small amount of super glue fixes the FlexiWeight permanently to the tube, which is necessary if you want to tie over the FlexiWeight. Pro Flexi Weight Specs X-Small/5mm (12 pcs/pk): 0.15 grams/2.31 grains Small/10mm (10 pcs/pk): 0.30 grams/4.63 grains Medium/15mm (10 pcs/pk): 0.45 grams/6.94 grains Large/20mm (10 pcs/pk): 0.60 grams/9.26 grains X-Large/25mm (8 pcs/pk): 0.75 grams/ 11.57 grains XX-Large/30mm (8 pcs/pk): 1.00 grams/15.43 grains **Pro Flexi Weight in sizes X-Large and XX-Large will be longer than the tying surface of a Pro Microtube** 10 per pack