Next time you are in the market for a carry-on bag, be aware that if you frequently travel within Europe or Asia on non US carriers the allowable size of your carry-on bag will be smaller. The two standard carry-on sizes outside the US are:
21.7” x 13.8” x 7.9” which is accepted by 70% of airlines
17.7” x 13.4” x 7.9” which is accepted by 90% of airlines
In addition, you will often only be allowed one piece of carry-on luggage, whether it is a purse, a briefcase, a laptop bag or a piece of luggage; as opposed to a US carrier allowance of two per person; one personal bag in addition to your carry-on luggage piece.
Finally, there can also be weight restrictions (possibly as low as 10 lbs.). Therefore before making your next carry-on purchase, determine the most appropriate size to fit all your traveling needs.