... screw / roof screw 1. Standards1. din75042. Material2. Stainless steel(SS304,SS316), carbon steel(C1022,1010,1008) copper, iron and so on.3 ... 7. After-sale service7. If any quality problem, we pay for the loose at once8. Surface treatment8. Black oxide, zinc plated ... competive price.3.material of our hex self drilling screw:stainless steel ,carbon steel,copper and so on4.surface treatment of this hex ...