This commuting backpack has very sturdy construction!  The fabric is durable and the waterproof liner will protect anything from leaking in or out.  I can fit my regular sized U-lock and my cable lock in the side pocket so they're really easy to access.  I'm only giving four stars because the backpack even when empty is a bit heavier than I expected.  I suppose that's the price you pay to have something that is constructed well.