13mm on the selector shaft, once that is loose get inside the car and move the gear stick about and the selector shaft will come away from the rod coming out of the box.
If you have trouble getting a tool on that 13mm, have someone hold it in gear inside the car as that will move about as you try and undo it.
If you want to remove the entire stick, 15mm adjacent to that which holds the tie shaft to the car and 2 off 10mm under the car either side of the bottom of the stick, move the heat shield out of the way first. Unscrew the gear knob and the selector mech will be free to leave.