Originally Posted by
Just Bill
The Ultra-sil version is the one I'm talking about.
I picked one up to try... the only reason I would use one is if it doubled as a pillow. It doesn't hold air.
Likely you could seam seal it and it might do the job, but I didn't care too. I use my real drybags this way when canoeing and picked up one of the bigger ones to try as a pack liner/pillow combo in Matt Kirk's Sub60 pack. The Ultra-sil is lighter than the bag that ships with his pack and using a large volume pillow would have been a nice combo with a Small size Neo air.
I haven't tried the e-vent one's, it's possible those are seam taped and if so would likely qualify as water proof, but as the e-vent "breathes" it would be waterproof but would fail the airtest by design.
That said, the air test is for submersion in non breathable fabrics is a good one... as mentioned, for backpacking I'd probably call them functionally waterproof.