These are great for trout-based leader set-ups and greatly extend the lifetime of one's leader. The smaller size works great for tight-line (euro) nymphing set-ups and even works for casting dry flies. If you are looking for rings to use for steelhead or warm water fishing, I'd recommend going with a bigger size to accommodate larger leader/tippet diameters.
Have used on tippet ring for multiple days of fishing and no issues. very durable.