Decide whether 50 liters solves the right problem
A claimed 50-liter backpack can hold a substantially different load from a compact school bag, but the number does not describe access or support. List the clothing, books, lunch and electronics that need to travel together, then inspect whether they can be separated without blocking the laptop. Leave unused room rather than treating the capacity as a target to fill.
Check the lock and airline wording separately
The current title mentions a combination lock and carry-on flight approval. Find which zipper pulls the lock controls and how it resets; it does not secure every pocket or prevent removal of the bag. Compare the stated 19.5 by 15 by 11-inch exterior with the current operating carrier and fare rules, because seller wording cannot guarantee cabin acceptance.
