Metric: M2 x 18 fillister head.
You can use a socket head screw as a substitute since fillister head machine screws may be hard to find. There's a good chance you will have to get a longer screw and cut it back.
Realistically, I usually buy bulk packs of longer screws in several sizes, then cut to length as needed.
Last edited by Andrew; 11-03-2013 at 08:26 AM.