Life-Flex (stretch floss)
By Hareline.
Strong stretchable floss that does not lose its color when wet or stretched. Superb for Buzzer, legs, Apps bloodworm.
How to tie the Apps bloodworm on YouTube (note: you can use ALL the available colors for this fly; not just red!!!):
https://www.youtube.com/watch?v=BJSFwKYmfOg