I recently purchased a box each of gallon and quart sized baggies with the intent of using my hand-operated vacuum pump (which pulls down to 27 inches of mercury) to pump them down and test them on a variety of survival bag goodies.

I figured by looking at the box they came in that the valve on the baggy would be ready to go--not true. Evidently, the proprietary battery operated vacuum pump offered for sale along with the bags has a method of penetrating the bag without leaving a hole for air to come back through smile

For now, the test/review is on hold until I get the device--I need to figure out exactly how it works.
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein