The .375" or 3/8" diameter was actually .393" and was too large to fit a standard 3/8" swivel nut or 6AN swivel. magnetic, but the Chinese version of zinc is more like cadmium. Update: Eventually the seller will realize it's really just a 10mm tube and sell it as such. Until then, beware his poor measurement and math skills, as the outside diameter minus two wall thicknesses is not equal to the inside diameter.