Question Hex Nut Size

[Googer]

There seem to be three common hex screw heads used in PC cases, one of which is 1/4 inch (largest), a smaller hex head for drive screws (what head size), and what hex head size are the brass standoffs?

The 1/4 inch, i have a few nut drivers for. The others I am looking to purchase.

 

[Googer]

One problem screwdrivers have is that one slip up and it can damage a PCB or Motherboard trace. This problem is eliminated when you use a nut driver.