Fred H.wrote a review of GSI Outdoors Collapsible Fairshare Mug on August 22, 2013
Familiarity: I returned this product before using it
Key words: "MUG", "LID". One would think you could carry a beverage around...
Snope! The model I received had a small silicone stopper in roughly the same location as the tiny pinhole in the lid barely visible in the product photo. On the plastic lid GSI inscribes: "PRESSURE RELEASE VALVE" (by the hole) and "NOT FOR STORING LIQUID".
This hole hobbles an otherwise tight locking seal at the lid to mug interface. I bought it to, I dunno, carry a protein shake to the gym in and then pack away. Sadly there doesn't appear to be a product on the marketplace to handle this sealable, collapsible cup problem despite this product's tease / promise.