square head bolts manufacturers Product Description DIN7991 SOCKET COUNTERSUNK SCREWS ITEM: HEXAGON SOCKET COUNTERSUNK HEAD CAP SCREWS MATERIAL: BOTH LOW CARBON STEEL AND MEDIUM CARBON STEEL DIMENSION: DIN7991 SPECIFICATION FINISHING: BLACK ZINC PLATED YELLOW ZINC PLATED HOT DIP GALVANIZEDsquare head bolts manufacturers website:http://www.hualongfasteners.com/other-bolts/