Use this as a guide to replace or remove the rear case.
Use tweezers to completely remove the sticker from the rear of controller.
Find the seven 8.3 mm Phillips screws on the rear of the controller and remove them.
Use a plastic opening tool to separate the rear and front casing by inserting it in-between the two cases.
Use the plastic opening tool to pry the two cases apart.
Remove the two rubber side grips.