I climb a lot on quarried granite, and these are invaluable for minimising rope drag when repeatedly changing direction. Once you have some, you end up finding all sorts of uses for them that you didn't anticipate beforehand, such as the first clip on a long sport route for ease of rope pull on lead. They are also a little metal work of art.
I've been using these since they came out they are very very good at reducing the drag on the rope, it sounds like you wouldnt notice it on a usual route but on their first outing I used two on a 20M pitch that I knew well, it did make a large difference
These karabiners are really useful. They look heavy but are surprisingly lightweight and the difference between these and normal wiregates is not a problem. They are ideal for use on the rope end of long quickdraws to reduce rope drag when your placemen