I put this little game together for Elinor the other day. At the store last night I saw the exact same thing for $20. Working at the daycare I remember making something simliar with an empty formula can (with a slit cut in the top) and the flat lid of a bottle.
I sat down with Elinor, showed her a ring and then put it in the container. She looked at me smiled and grabbed another ring right away to hand me. After a couple more I handed her one to try. She is still working on her coordination to get it in but is doing great!
I walked away to start dinner and she sat working on it for 15 minutes! 15 minutes of silence! Normally that would make me nervous but she was busy playing. We were working on colors while putting them in today and she seems to have picked up "blue". According to her every ring is blue.