... .Grade:4.8 ,6.8,8.8.. Special screw,special head screw,special machine screw 1.What’s the specification of our Products ... a professional manufacturer with more than 20 years experiences in screw,bolt,nut,washer,rivet, stud, pin,wrench and so on ... control from producing to delivery.Our company had strong technology support,a special quality control procedure,have some special persons in ...