Interesting hobby. ;-). How is the weight of Yunzi compared to the others? I like the shape of these melamine stones ( https://www.amazon.com/gp/product/B000Y9PD04/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 ), but they are too light.

Maybe I should look into a new set of glass stones. Do they also come single-convex?

What's the cheapest I could expect to find shell and slate?