Pls reference bag outer and inner dimension ( Length x Width x Thickness ) before your order it.

11.6 inch bag :  Outer dimension : 315 x 205 x 30 mm.  Inner dimension :  300 x 195 x 25 mm.
13.3 inch bag :  Outer dimension : 345 x 245 x 35 mm.  Inner dimension : 330 x 230 x 30 mm. 
15.4 inch bag :  Outer dimension : 390 x 285 x 40 mm.  Inner dimension : 380 x 265 x 35 mm.     
15.6 inch bag :  Outer dimension : 400 x 290 x 40 mm.  Inner dimension : 390 x 270 x 35 mm     

11.6 inch bag is a little big for macbook 12 inch, pls make order if you can accept a litter big size bag.

13.3 inch bag is very big For Macbook New 13.3 inch, A1706, A1708, A1932, A1989, A2159, A2179,  pls help do not order 13.3 inch bag for macbook new 13.3 inch and other brand Ultrabook 13 inch

13.3 inch bag is perfect fit  For Macbook model  A1466.

13.3 inch bag is not good fit for all brand laptop 13.3 inch,  Such as For macbook new 13.3 inch, own thin screen frame, the laptop outer length is 304 mm,but for macbook old 13.3 inch laptop outer length is 325 mm.

14 inch and 15.6 inch bag is aslo cann't perfect fit all brand laptop 14 and 15.6 inch, they all need reference laptop length and width diemension.

Ultrabook 13 inch laptop may need choice 12 inch bag.
Ultrabook 14 inch laptop may need choice 13 inch bag.
Ultrabook 15.6 inch laptop may need choice 14 inch bag.