There are three containers. The smallest has a gasket seal and a special gasket vent in the top and is intended to hold the food you want to keep hot. The middle container is meant for rice (though you don't have to use it for that) and has an insulated lid. It sits directly above the hot container, so the heat from the hot container will warm through the rice container while preventing the top container from getting warm. The top container has a handy insert to divide it in half; its lid also has a gasket and it screws into the outer lid, so it's pretty much watertight.

The specs from the booklet put it at 840 mL (soup bowl: 6.8 oz; middle bowl: 10.5 oz; divided bowl: 11. 2 oz.) but I measured it when I got it and it came out closer to 710 mL to 770 mL (24 oz to 26 oz) if you measure to the levels you can actually fill it.