WAVE PLATE HEAD SCREW 1.ISO,ANSI,JIS,DIN,BS& non- ... 3.Grade:4.8 ,6.8,8.8,9.8........ WAVE PLATE HEAD SCREW,DOUBLE HEAD SCREW,KNURLED HEAD SCREW A ... quality 1.The material are always use C1022 ,The percent C element is 0.18%-0.23% ,is higher hardness than ...