I have a PRS 25 and have been wearing it on a simple pull through strap but I would now like to resize the bracelet so I can fit it to the watch head.

What size screw driver should I use?

I have some cheap/made of cheese ones but the previous owner may have used a thread lock on them and they appear to be very tight to unscrew. I would like to make sure I have the correct tool rather than destroy the screw/bracelet completely using a cheap tool that is the wrong size!

Thanks