£1.99FK Caddis Dry Flies x 3 

If you look at the fly in the water, reflection in the surface film makes me believe this is one of the reasons why the fly is so successful.

It gives double the normal "profile" for the fish to zoom in, plus you have the added advantage of the hotspot, which is a great attractor for the fish.  The F&K Caddis can imitate an emerging, hatching, trapped caddis, with the submerged abdomen.​​​​​​​