Duffel bags are a great alternative to suitcases or backpacks and are designed to fit as much as you can comfortably carry. Whether you’re looking for something small to carry on the plane, or a massive beast of a bag with wheels to pull behind you, there are plenty of great duffel bags to choose from. If you’re planning on being airborne with your duffel, it’s pretty important that it meets the carry on requirements of your airline. This way, you no longer have to worry about checking your bag into the hold, and you’ll always have your personal belongings within easy reach in the cabin. Small duffel bags will offer between 25 to 50 liters of usable space, and most of them will meet the 22 x 14 x 9 inch specification for most major U.S. airlines. These smaller duffel bags are pretty useful for weekends away, solo travelers, and those who only like to pack the bare minimum. If you think you need a little more space to carry your kit with you, consider a 50- to 75-liter capacity bag. Perfect for those who need more space for extra layers, but aren’t worried about carrying bulky equipment, most of these medium-sized duffel bags will need to be checked in when you fly.