Seriation Toy

I found these little cans at a dollar store. Three round tins and three square tins.
Inside the smallest ones I placed a round toy cookie and a square toy cookie.
The language I overheard parents using included small, medium and large, put it in, take it out, which one is next, different shape.
It was fun to watch them experimenting with stacking. They enjoyed when the tins tumbled down.