Clip-on Plastic Book Supports 6 1/2 inch - Orange

I thought these would be just the thing to keep my books tidy--I have a considerable number of books, and like to separate them by subject. However, the plastic used is on the light side, so while the bookends clip onto shelves well enough, removing more than a couple of books causes the rest of the books to tip onto the bookend and push it over a bit. I think if the plastic used was heavier and thicker this wouldn't happen so easily. However, they DO tidy up books and keep them more neatly arranged. I just wish they were a bit sturdier.