... 20 years experiences in screw,bolt,nut,washer,rivet, stud, pin,wrench and so on .2. Our company had good reputation with ... is strong not break when you tighten the fasteners by wrench ,key ,bit and spanner.When head become thicker,and then ... other manufacturers,it is convenient to tighten the fasteners by wrench,,bit,key etc.3.The scrows are also much deeper ...