Durable O.P.SAK 100% odor barrier bag. No gusset. Store food undetected at the camp site. OK to add boiling water to the O.P.SAK to prepare food as the film is FDA approved. You can not place the O.P.SAK in boiling water. The O.P.SAK uses the same seal as the ALOKSAK and offers all of the same air and water proof features. If you need a storage and transport bag that is tolerant to extreme heat, the O.P.SAK is the bag for you. You can use the 5.1 with the 9 X 10 OPSAK and he 8.6 with the 12.5 X 20 OPSAK. Tested and approved by: SSI (formerly NASDS) certified waterproof to depths exceeding 60 meters. Confirmed testing in their pressure chamber under constant pressure of 200 SFW for two weeks without leaks. US NAVY Passed submergence/thrash/pull tests conducted by Navy Experimental Diving Unit. North American Fishing Club Approved after being diversely tested by a selection of 35 individuals under a variety of circumstances.