I initially purchased this "carry-on" bag to meet WOW airlines rule of one small carry-on per person. This bag was perfect for my 4 days in Brussels and I was pleasantly surprised by how much the bag can actually hold. There was plenty of space not only for my clothes, but my ankle boots as well! Everything fit perfectly and it does indeed fit underneath the seat! My daughter even carried this bag when we went to Barcelona and it is still holding up just fine! I absolutely recommend this bag especially if you're flying on an airline with baggage restrictions for carry-on.