*11 12 inch: for Macbook air 11.6 inch,retina 12 inch
*13 inch: for Macbook air/pro/retina/new pro 13.3 inch
*15 inch:for Macbook pro/retina/new pro 15.4 inch
Note:If you order it for other laptops, you could choose the size referring to the following picture. Please know that this bag is a bit bigger for Macbook new pro 13 touch bar and no-touch.