Well, I don't know about yours since I don't know which ones you have but on mine, if you're standing at the front, looking toward the rear, there are two hex screws on either side of the mirror. I took those off and the mirror split in half, there was a screw inside the half that remains attached to the bike around the ball and socket that could tighten a slider piece that made up half of the socket.
Does that make sense? In other words, half the socket is built into the mirror housing, the other half is adjustable with a screw. Could have been a hex as well, it's been a year so I'm fuzzy.