Choose from M3, M4, M5, M6, M8 thread sizes. A2 Stainless Steel Button Head Socket Screws. M4,M5,M6,M8 A2 Stainless Steel. M3, M4, M5, M6, M8. M5,M6,M8,M10 A2. Allen key size: 2mm. Manufactured from A2 stainless steel for improved corrosion resistance.