Well. I bought this bag before reading all the reviews and am sad to hear that its common for the clip to break. My question is, does it mostly happen when its clipped into a mountain bike? I could see how all that jostling would break the clip. I do a lot of road riding and If mine breaks I'll update this review.
That being said, I love the design and chose the smaller bag of the two Fizik makes. I can fit a spare tube, multi-tool, tire levers, and a CO2 cartridge but its a tight fit. Previously I had a specialized velcro bag that always bounced around and was difficult to get into but this bag holds firm to the saddle and is easy to access.
UPDATE - 2/17/2015 - the fizik bag snapped off from the clip, true to all the other reviews. It happened when I rolled off a curb with much force - kind of depressing that it couldn't hold up. I'll be reaching out to fizik regarding warranty. That being said, I'm not sure I would recommend this bag to anyone else based on this break.