Diawl Bach flies are generally used just under the surface on a floating line and long leader. They represent various nymphs which trout find attractive and are very successful flies for catching trout and grayling. This set is a slimline version tied on medium weight Kamasan hooks by myself. They are designed to fish just sub-surface to either cruising trout, or trout that are searching for insects trapped near to the surface. Ideally they can be used with floating or intermediate lines and long (i.e. 12-18') leaders.