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For this project, I used the Cocobolo interchangeable from Knitpicks. Wood.
But my new favorites are the ChiaGoo. My daughter in law bought me their large interchangeable set for Christmas. It goes from US 2 (2.75mm) to US 15 (10mm). Metal. Totally love it

Ah, I must check them. Thanks!

Be prepared for a sticker shock. They are expensive. And do not buy them from Amazon. Apparently, there are a bunch of fake ones on sale there that are really low quality.