This might not be the saddle bag for you if you are the type that wants to be prepared for every possible situation (multiple tubes, multiple CO2 cartriges, tire levers, chain tool, spare chain links, multi-tool, spoke tool, etc...), but it works great in the vast majority of situations. If I was doing very long distances solo or had no backup way to get home, I might get something bigger.
I have mine filled with a spare 25mm tube, tire lever, co2 cartridge with leather cover, co2 head (PDW), a valve extender removal tool (tiny), and there is still a small amount of room left.
Only negative I have found is that the strap that holds it to the saddle rails is a little short. I'm only getting about 2cm of overlap of the Velcro. Perhaps I am just not pulling the strap tightly enough but it does not move around under my saddle when attached.