Great for mini albums or holding cards or bits of things together. I've not broken one yet. On occasion I have trouble opening it (if it opened too easily things could fall off the ring unexpectedly).
I used the rings to hold simple addition equations together. The students use homemade manipulatives to make a visuaal representation of the equation. When I bought this product I was really looking for plastic rings that are about a half inch diameter but you can only get them from teaching supply catalogs.