Hareline Bead Chain Eyes are meant to add weight to fly patterns. They are popular for bass patterns, streamers, and saltwater patterns.  A great use for bead chain eyes is when you want to control the orientation of your hook underwater.  If you want your pattern to ride hook point up, simply attach your bead chain eyes to the top of the hook shank.  The chain will not tarnish, is great for saltwater applications, and is made out of quality material.