The Blue Winged Olive is used on long thin leaders, a fly to go to when your using a fine bamboo fly rod casting to sipping trout. If you cant see the smaller sizes at distance tie the blue winged olive off an attraction fly you can see like a fluffy caddis. I usually tie it off 18 inches and watch the attractor fly for jigs or movement or a swirl 18 inches trailing it. Keep the drag free float on the attractor assures usually a drag free float on the tiny bug behind.
