Pls reference the bag outer dimension ( length x width x thickness ) before your order it. 13.3 inch bag : Outer dimension 365 x 260 x 40 mm , Inner dimension : 330 x 230 x 25 mm . 14 inch bag : Outer dimension 395 x 295 x 45 mm , Inner dimension : 365 x 255 x 30 mm . 15.4 inch bag : Outer dimension 400 x 300 x 50 mm , Inner dimension : 370 x 260 x 30 mm . 15.6 inch bag : Outer dimension 435 x 310 x 50 mm , Inner dimension : 390 x 285 x 35 mm . 13.3 inch bag is just can perfect fit for macbook old 13.3 inch ( laptop length 325 mm), 13.3 inch bag is big for macbook new 13.3 inch,2016-2020 Pro 13, 2018-2020 Air 13, M1 13 inch ( Such as : model A1706, A1708, A1932, A1989, A2159, A2179, A2251, A2337 ), pls make order if you can accept big bag. 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. Pls kindly contact with us if you cann't sure which size bag is fit for your laptop.