I just envisioned it being a cup to sip hot or cold beverages from but never made use of it....if it did have purpose I'd love to hear it, tea mug? I think I was daydreaming. The weight is nice and an alchy fuel bottle will fit in it.
Ken, unfortunately that is a rubber band.....if I could find silicone at that size it would be nice. I don't think I've tried hard enough. I'm not convinced reflectix would save on weight when given the tape, but I don't argue it would be more efficient.
Fyi, I also had a version of this in 24oz. Fits more stuff inside that's for sure