I use a few different boxes, depending on what I'm bringing, e.g. if I'm bringing sauce and rice separately I use my little samurai (he gives me extra room for a bowl of soup too!). The other boxes are mostly the same size, 400-500ml, which is perfect for me, except for my large black one but I only use it if I know ill be too busy to have a snack or if dinner will be a lot later, even then I rarely finish it all if it is packed tightly.
I stick to plastic boxes, as glass would be way too heavy and I worry that I would wreck a fancy wooden one.
Check the last post for a wee nosey at it.