A couple of years ago Doug Freemann showed me this fly after having been introduced to it by the guys he competes with on the US Youth Fly Fishing Team. It's another one of those simple but very effective flies that can be used to imitate just about any fly just by changing the color of the body and/or the hackle. This past summer I gave it a good workout in Montana having tied it with a pale yellow body and dun cdc hackle for the PMDs, and it fished very well. I also did well with a tan bodied, natural cdc hackled version in the evenings to imitate the tan caddis that hatch on the Madison River.
The video shows a Blue-winged Olive imitation, and with the level of clarity that Tim gets, you can see how the cdc feather is covered with tiny barbs that catch air and also provide plenty of surface tension to keep it afloat. I recommend that you use your thumb nail to shorten the cdc fibers rather than using your scissors so you get a very "buggy" looking profile. Tie some up in sizes #18-24 for the fall hatches of Olives. You'll be glad you did.
Sharpen your hooks.