There is also German tubing in common US sizes. I haven't bought from Spruce for several years but I think they sell both US and German. Wicks had a huge supply of Chinese, they now claim to sell only US. One other issue to be aware of is 4130 flat stock. Most designs call for 4130N, but there is still 4130A(annealed) being sold. In small pieces, especially narrow strips, it may not be possible to read the markings.