A sharp hook can be the difference between you and your trophy. These hook hones are a critical piece of gear for any angler. Treated with deep penetrating long lasting rust inhibitor. Both style files are double sided. One side is coarse for heavy work or resizing a hook point. The other side is more of a fine grit for retouching a hook and applying that needle sharp point you desire.Great files for the money! The smaller style file is great for heavy freshwater flies and most saltwater flies and smaller hooks to 1/0 size.