For a mayfly, the straight shank of the HDD 301 defines the line of the abdomen between the cerci and the thorax. Choose the hook size based on the length of the body, then scale the hackle and wings accordingly. With this standard thread, keep the tying base thin: excess thread and dubbing add weight to the dry fly. The hook is made of high-carbon steel, with a chemically sharpened, barbless point. It features a Black Nickel finish and comes in a pack of 25.