I make keychains out of wood and needed a restock of rings. i have seen many different sizes and costs and this was actually one the sets i was looking at. gave them a try and they fit perfect. its a thick metal ring unlike the last set i had that was thin copper almost which just bent. this will hold up well to abuse and keep your keys or in my case keyrings safe. these are roughly 24mm and are easy to use. I look forward to ordering more of them.