This is an adapter used when the size of a "seiro" (steamer) and a "nabe" (pot) don't match. Inner diameter of the pot: 20cm Outer diameter of the steamer: 10cm to 18cm This is a stand for Chinese steamers with an outer diameter up to 18cm. It can be used with pots with an inner diameter of 20cm. (If the pot doesn't have a handle, it can also be used with smaller pots. It's like the image in the 5th picture.)