Kinda long term review and probably late, as I have the bag in pretty much unchanged state content wise for more than 2 and a half years.
Basic idea was to avoid having tools taking space in the jersey. At that time I did not have the bladder backpack, so often I would put the second bidon into my back pocket.
It performs well, it is packed to full extend, so some Lego-fu needs to be done when placing the stuff back in. But on the same time the fullness, prevents rattling.
It failed only once, when BOA dial got loose on a clean gravel path, fell into my tire and while I noticed and stopped, I have burned a hole in it.
Waterproof promise did not held up, so I pack insides with a nylon bag.
Silca Mattone