I was so excited for this backpack because I love the quality of the fabric, the versatile use possibilities of the bottom compartment, and the internal bottle feature (it's SO hard to find cute backpacks that can secure a 32 oz. Hydroflask inside the backpack without being $200+). However, the 13.5" laptop capacity can be misleading if you don't think of it in terms of actual laptop size (as opposed to the common advertised sizing for most laptops, which go by screen size). Unfortunately, I didn't even stop to think about that sizing discrepancy, so I was disappointed. I have a 2015 13.3" MacBook Air, and it just barely fits; the corners jut out a bit at the top of the backpack when it's closed, which I'm not a big fan of in a backpack at this price point. However, I wanted to use this primarily as an EDC work backpack to fit my slightly thicker HP Elitebook work laptop. It's roughly the same size in terms of length and width compared with my MacBook, but of course, it didn't fit at all (I couldn't zip up the backpack). Overall, I really wanted to love this, but it just didn't work out for my purposes, so it's going back. But to be completely honest, as far as laptop sleeves go, I'm also not a huge fan of the mesh front panel because it's not very protective, so using a laptop case would be necessary in my opinion.
Overall, if you have a laptop that's closer to 13" or smaller in terms of actual physical size AND you have a case for it, then this backpack would be perfect. I personally think that size capacity is too small as a standard though if only one size is going to be for sale. But if Popflex ever releases a bigger size, I'd probably buy it!