Just to add to my comment above (I can't edit it because it's anonymous), my MacBook Pro is a mid-2015 15in model 2.8GHz (A1398; EMC2881). For the bottom case it uses six 3.1mm screws, and four 2.3mm screws at the clutch/hinge side of the MacBook Pro. I tried using a 3.1mm screw at the clutch/hinge end, as described in the main article, and they don't fit. It has to be four 2.3mm screws.
The number of screws listed here is wrong on my model. I had four of the smaller size.