Matein Carry-on Backpack 40L

The Matein is one of Amazon's best-selling travel backpacks for a simple reason: at $30-45 it turns the free personal-item allowance on basic-economy fares into a functional weekend bag. Its 18 x 13.5 x 8 inch dimensions duck under most US airlines' under-seat limits, the main compartment opens wide enough to pack deliberately, a padded sleeve takes a 17-inch laptop, and the USB pass-through port — plug a power bank inside, charge outside — is a genuinely handy touch at this price. At 2 lb 1 oz it is the second-lightest bag in our ranking. The score reflects the honest ceiling. The advertised 40 liters is marketing: those dimensions compute to roughly 32 liters, and owners consistently describe it as smaller than expected. The polyester shell, thin straps, and token back padding are built to a price, water resistance is light, and there is no hip support or frame of any kind — this is a bag for getting from A to B, not for a mile of cobblestones. It sits last in our budget travel backpack ranking because every bag above it is more bag; it stays in the ranking because nothing else converts $35 into avoided baggage fees as reliably.