Allen Wrench for Magpul ar15 trigger guard

whats up gunsmith, what allen wrench fits the magpul Ar15 trigger guard i have went through every allen wrench i have, is it metric or millimeter and what size??
thanks in advance
so frustrating

1/16" hex wrench will seat the screw.

Im not trying to contradict what execprotect said, but I believe it may be metric. I just put one on sunday and the allen wrench I used was a small sae wrench, it may be the size he said. I do not remember the size, and I'm to lazy to walk to the truck to see. Anyway the wrench worked but it was not a exact fit. I remember thinking it must be a metric wrench but this worked so I said the Hell with it. But in my honest opinion I think it is a metric screw.
You would think they would tell you on the package. I bought mine from midway and I thought in the description it said it came with the wrench. I could be mistaken on that also, as it arrived by pony Express lol, so I'm running on memory from several months ago.

The spec screw is 1/16. No metric screws on mil spec AR's.