The flexx of UNI products is an elastic multi-fiber flat wire. Once tyed on the hook you can stretch it to get the desired section. It is often used for tying buzzers body and or cheeks. Many used for tying whitefly flies.
The body gills or furry foam in the form of hairy foam that is cut to make nymph bodies. After cutting separate the two faces. The chartreuse fluo is often used for making green worm (a delight for chub and trout).