Choosing a carry-on is as simple as knowing the exact dimensions you can fly with (find any airline on this list) and finding a suitable bag you like. Unfortunately, the sizes aren’t standard across all carriers. The general rule is that domestic carriers are a bit more lenient while international carriers can be very strict. Still, it’s always best to err on the side of caution. There are some amazing bags at equally amazing prices, check them out here before you buy, and be prepared for your next trip.