Osprey Daylite Duffel Bag 60L - Lightweight Travel Duffel for Hiking, Camping & Gym - Water-Resistant Carry-On Luggage for Men & Women

Good balance of backpack&duffel. Suitable for air travel.60L is a good size, big enough to hold multiple days clothes, but not so large that it's hard to wear or maneuver while wearing. For my height ("average" American male), I would not go smaller than 50L or larger than 70L. It's small enough to pack into a larger suitcase if you're not sure how much capacity you'll need on the way back.Very well made, no dangling bits, heavy material, and multiple handles. The straps are not the most padded and there's no sternum or waist strap (it's not an actual backpack) but perfectly adequate to wear as a backpack for making connections & transits. Mine went through multiple international airports as checked baggage and shows no sign of wear.Other Thoughts: Make sure you load it correctly if you plan to wear it-- extra weight on what suddenly becomes the "top" is very awkward. The airlines I used put the duffel in a luggage bin both for checking and for baggage claim. The small side pockets (curiously only on 2 sides, instead of 3) are handy.Quibbles: shoulder straps should be a little more padded. A loop to allow hanging this off a large suitcase would be helpful for air travelers.Overall, the best of 3 similar bags I looked at. And I've been very happy with the longevity of my other Osprey backpacks. Recommended.