International carry-on size restrictions can be notoriously challenging since so much of the restrictions are determined by where you are traveling. Here's a breakdown on just what to look for with your next trip.
Outside of the U.S. the standard carry-on baggage size is smaller (this relates to flights originating outside the U.S. and with a destination outside the U.S.) Here, the rule of thumb is about 21", and not the 22" and above carry-on size. As with any rule, exceptions abound and it is a good idea to visit the site of all of the carriers you plan to use while abroad to get a consensus. If you travel outside the U.S. on a regular basis or are looking to purchase a bag for someone who does, you might want to consider replacing the standard domestic sized carry-on bag in your set with an international carry-on sized bag. In terms of what the two bags will actually hold the difference is not that great and it may add some flexibility in your travels.