These nicely made little nickel plated steel screws will go where others will not, like on some Gretsch Electromatic guitars with tiny, tiny tuning machine mounting holes. Be careful when you install them not to over tighten or you'll rip the head off. I measured exactly 2.1mm on the main threaded portion of the shank. Length of threads is around 8mm. Head diameter 4.38mm. A set or two is a must for your roadie kit of parts.