1. Standard with hex head
Standard size, uniform force, placed in the middle of the head without displacement, not easy to slip
2. Obvious threads
Uniform pitch, obvious thread, no burr residue, threads of set screws will be able to get good grip
3. Come in many different sizes
The screw size is difficult to measure without professional tools, and the range of screw sizes and other fasteners is exhaustive, many of them are very small unknown gauges, thread pitch, etc. a set of screws you will get several other boxes with different screws, so you can always have the right size for this kind of thing