Flash, thread and a bead _ it's remarkable that a fly so simple can be so productive.
David Knowles is a long-time Arkansas fly designer and commercial tyer, who developed this pattern. There are no substitutes.
This fly has been one of our top producers for years. Silver bead designates it as tungsten. One size only (#18) _ if you need another size you aren't doing it right.
Our guides have used this fly often to put clients on fish around and over the 24" mark.