45L Peak Design Travel Backpack can be used as an everyday bag carry-on or checked bag for all your travel needs. The default 35L backpack configuration meets the maximum international carry-on standards so you can fly with confidence. Or if you need a little more space double zippers provide an additional 10L while durable face fabric and ultra-lightweight foam lining keep your gear protected so you can safely check your bag. And vice versa Compression buttons reduce bag volume to 30L when you go on a day trip and plenty of internal and external pockets help you keep all your gear organized throughout your trip wherever it is.