Designed as a Crappie jig, but catches almost anything that swims: Bass and Panfish will devour it. Trout, especially in lakes will take it. I've even caught Walleye, Northern, Catfish, Perch, and Eel Pout with it. Use the 1/100th, 1/80th, and 1/64th sizes on a fly rod and the larger sizes on light spinning gear. This is my standard dropper fly on a two fly trolling rig for lakes but it also casts easily.
I occasionally tie some up in black (but still using the fire orange thread) which conventional wisdom would say should be more effective on Bluegill. They work, but I don't think they're as effective as the fire orange version.
Be sure to wrap the tinsel yarn down right behind the neck with quite a few turns of the fire orange thread. Ron claims this suggests a gill. There are whip finishers designed for jigs, but I've never gotten the hang of using any of them and just tie the whip finish by hand.
The nickel jig heads are available from Cabellas as 31-9059 Nickle Plated Fly-Tying Jigs. Wapsi Lists them as JHP080 Jig Heads Ball Style, Nickel
The Body material goes by "Tinsel Yarn", "Sparkle Tubing", and "Sparkle Braid". You can find it Craft Stores as Metallic Needle Point Yarn, Size 10. It is a rough metallic tubing, but is wrapped on the hook like a yarn or chenille.
I've seen Nickel Jig Heads in larger sizes, though Cabellas doesn't seem to carry them. Above an 1/8th of an ounce, Ron generally adds a Fire Orange crosshatch "ribbing" to the silver body and sometimes adds feather or bucktail wings.