I bought this for rooibos and herbals. It does an excellent job of keeping fine particles out of my cup. This is the medium sized Finum. It fits perfectly in my 12oz mug. Clean up is easy.
When I discovered it also fits well in my 6oz cup, I started using it when doing small quick steeps of 3-4oz in a quasi-gong fu style. I don’t own a gaiwan so this does a good job as a substitute.
This works so well we bought another. One or both are full of leaf all the time. I can think of nothing that needs changed unless it would be to make the plastic parts out of stainless, but then it would probably be a lot more expensive.