Scope Werks Turret's set screw size?

Good afternoon. Can anybody tell me the thread size of the set screws that hold the Scope Werks turret in place atop the scopes regular turret? I can't see inside the hole to see the size and I've tried both metric and standard alllen wrenches with no success. I don't want to strip anything and Eric is away on a hunting trip. Thanks, Stoti