DIN557C Square Nuts Product Grade C 單倒角方螺帽 C型 Thread M4 M5 M6 M8 M10 M12 M16 M20 P 0.7 0.8 1 1.25 1.5 1.75 2 2.5 m 3.2 4 5 6.5 8 10 13 16 s 7 8 10 13 16/17 18/19 24 30