Hollow Silicon tubing which has a huge range of uses:
A short length can be threaded onto hook, (round the bend) over say a bed of different coloured thread or floss..
to create a semi-transparent body very indicative of fish fry, nymphs, etc..
It can be caught-in and pulled tight and wound to create very realistic, segmented bodies for nymphs, buzzers, etc..
You can thread any type of wires or tinsels though the centre to create some amazing body effects..
Or you can even use it for detached bodies on dries