Along with being 100% water/air tight like our ALOKSAK, the O.P.SAK (Odor Proof SAK) is also a 100% odor barrier bag. We use the same seal on our OPSAK – no gusset – that we use on our ALOKSAK, but with a different film that is odor proof and FDA approved. You can store food undetected to bears and other pests in your campsite by sealing them in the OPSAK. Also, because the OPSAK is FDA approved, you can use it in food preparation and storage. You can even pour boiling water into the OPSAK because of its extreme heat resistance. See below for product details.