The HDG 644 accommodates the bodies of gammarids and larvae, which conform to the curve of the shank. A flexible back accentuates this line, while a wrap maintains the segmentation of the fly. To choose the size, consider the length of the abdomen along the curve: it does not directly correspond to that of a straight hook of the same size. Its downward-facing eye distinguishes it from the HDG 645, which has a straight eye. The HDG 644 is barbless, features a Black Nickel finish, and is packaged in packs of 25.