A2 Stainless Steel Self-Locking Nuts M3-M20 Metal Insert Lock Hex Nuts GB6184. 304 stainless steel, suitable for outdoor or humid environment, corrosion and acid resistance. Thread Dia:M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20. According to your choose. Please list your special requests color, packages, etc. (15-35 Days to Delivered). Please contact me before you return it. Not accept returning of electronic components. Feedback is very important to us.