201 Stainless Steel (SUS), suitable for use in a dry environment, it is easy to rust with water.
304 Stainless Steel (A2), outdoor or humid environment, resistant to corrosion and acid.
316 Stainless Steel (A4), added molybdenum, more corrosion resistance and pitting resistance, especially suitable for seawater and chemical media.
These nuts see photo 2 for detailed dimensions.
The data is a single batch, manual measurement, there are errors!
The color of the photo may have a color difference due to the monitor!