I bought a set of these for a Lemond I did a custom build on, primarily because I couldn't decide on a traditional bottle cage that I thought looked right. Fabric now makes these bottles in two sizes: 600ml and 750ml.

I've got about 200 miles on my Lemond using these bottles, so here are my takeaways:

1. Removing/replacing the bottles while riding is more difficult than a traditional setup, but not as hard as you'd think. The ovular shape helps you align the bottle, and the entry slots are wide enough that you don't have to be exact. I'm at the point where I can remove/replace without having to look down. That said, I'm not comfortable enough with these yet to put them on my fixed gear bike.

2. The valve is sufficient, but not of the same quality as a Camelbak bottle. Unfortunatley the bottle opening is sized just differently enough that a camelbak lid won't fit.

3. The more you tighten the mounting studs, the more secure the bottle becomes -- and conversely, the more effort required to seat the bottle. I don't do gravel riding, but I do ride one some pretty rough roads and haven't lost a bottle yet.

4. They're a good solution if you're a weight weenie, or you can't find a cage that you like cosmetically.