I'm surprised and very happy with this bottle. First off, it's titanium (if you're looking at this product, you probably already know about how awesome this material is). I was halfway expecting this bottle to be easy to dent like the other titanium bottle I bought from this company over a year ago, and even if it does do that, it's a trade-off for the lightweight... it's worth it to me. However, they've beefed up the most-likely-to-dent points for this bottle! It feels solid to me, nice attention to detail Keith Titanium!Now here's the awesome thing with this bottle... The ingenious use of a silicone insert (that stays put, horray) in tandem with a little vent at the top of the cap (see pictures). You all nailed this! It's such a simple thing to keep clean/clear and prevents altitude changes from affecting the bottle. It's like the vargo titanium bottle, but better. The risk to this sealing system would be losing the silicone seal, but that seems hard to do and also easy to replace if it happens.Nice product overall, I'm using this daily as well as for trips like backpacking, hiking, etc.