I have the Ortlieb Back Roller Classic panniers and highly recommend them. They hold quite a bit. As an example I carry a full change of clothes on one side with plenty of extra room left over. On the other side I carry a large hard lined lunch bag and extra outer wear gear if I need it, also with extra room. I do not carry a laptop, but I could if I needed to and these bags are completely waterproof, a good thing, especially if you are carrying a laptop.