1.ISO 9001 certification 2.DIN,ISO ,JIS ,GB,ANSI standard 3.stainless steel,carbon steeel 4.high quality,competitive price producthex nutsstandardDIN 934 GB52 GB6170 GB6172specificationsM6-M64 1/4 -2''size--material304 302 321 201 667 668 316 316L, hex nuts DIN934-A2