Metric DIN 934 Plain 18-8 Stainless Steel Hex Nut, M3-0.5 Thread Size, 5.5 mm Width Across Flats, 2.4 mm Thick (Pack of 100)
Most often used on machine screws and threaded rod, these general purpose nuts are for low-strength assemblies.  Hex Nuts have flat tops with chamfered corners; bottoms may be flat or chamfered.  Hex drive systems are driven with a wrench.Tensile strength of this material is 12,000 psi (pounds per square inch).A threaded fastener's size name includes information about the major external diameter, followed by the threads per inch, which indicates if it is coarse or fine.  Coarse threads are better when working with brittle materials; they are sturdier and are easier to thread and unthread compared to fine.  Coarse threading also allows for thicker coatings and platings.