The tungsten wire is perfect for give an extra weight to small and super small nymphs and buzzers. Sometimes tungsten beads can scary the fish and the lead wire is too thick to be used. A tungsten wire is perfect for this purpose and more than that is non toxic like lead is. It is good to know that some rivers is not aloud anymore to be used weight made of lead!
We use this wire like a thread/body thread especially for small nymphs with or without nymphs. In this way the siluethe will remain slim but the weight of the fly will be high ( for example for a perdigon tied on size #16 hook with a tungsten bead of 2.5mm the final weight was with almost 25% higher! )