The thermos jar appears to be indeed of 304 stainless steel since it didn't develop rust under my six weeks of use. It's double-wall insulated and has a volume of 8 oz. I trust their claim to be BPA free and it has a silicone gasket to seal tightly, so the plastic doesn't even come in contact with the food. Food grade silicone doesn't contain BPA, phthalates, lead or BPS. Many BPA free plastics still contain BPS which is equally toxic for us. Hence I prefer that no plastic at all touches the food. The handle of the lid lies flat to save space and to open the lid, I just lift the handle and push it down to close. I've never had a leak with it for the 6 weeks I had it. I’m a ramen fan and mostly prepare and store organic whole wheat ramen inside my jar. I learned from using it that it keeps soups and similar liquid meals warm or even hot for up to six hours when I follow the instructions and pour in boiling hot water. However, as it is made of steel, I can’t heat up my meals inside the microwave. On the other hand, I can place it inside my dishwasher to clean it.