ANSCO's high quality socket screws

Its strength is three times as strong as machine screws, which is the strongest level among the general standardized screws.
It has a hexagonal hole on the head. Usually, it is used without any nuts.
Because of its great assemblity and breakage prevention,it is used for fixing machine tools, automotive parts etc.
Usually, its surface treatment is black oxide.
May be tightened with a hex allen key wrench.
Compared with hex bolts, its head size is small.
So frequently its head is sunk into spot facing to save a space.