Remove the left 3 mm and right 8 mm (right screw is unnecessary to remove on some models)

One 3.25mm Phillips #000 (Head: 4mm dia. x .5mm thick)

One 8.5mm Phillips #000 (Head: 4mm dia. x .75mm thick

The Phillips screws securing the MagSafe board and the left speaker to the lower case. The next two speaker steps are unnecessary one some models as are steps 16 and 17 as the magsafe will drop in without removing these.