Screwdriver for 13-inch MacBook Pro
Here, according to iFixit Tutorial for a MBP 13" Late 2011, for the case, you'll need: 


Three 14.4 mm Phillips #00 screws 
Three 3.5 mm Phillips #00 screws
Four 3.5 mm shouldered Phillips #00 screws


If you need more information about others screws, please refers to others tutorials on this website about what you wanna change.