These are the best and perhaps only "keyhole style" rivet hangers for big wall climbing. They are essential for nearly any big wall rack unless you are doing a "Super Trade Route" like The Nose or Moonlight Buttress. When you use one of these, you are usually in a place where you are really glad you have it!
On a route with many hangerless bolts, these will make a giant psychological and safety difference. With these keyhole hangers you will feel secure. With only wire rivet hangers you can feel like a strong wind gust could blow off all your protection.