Great quality - not too big
I ride a BMW S1000RR and was looking for space to put "stuff". This seat bag fits the bill. It fits my air compressor, flat fixer, various little tools, zip ties, air gauge, all without expanding it! And it fits right on the rear seat.
The build quality is exceptional.
Only a couple of peeves. One is the mounting/install instructions are very sketchy, and the other is that it is mounted using straps that loop around holders. Not being able to see it when I am riding, I am constantly scared it might work itself loose somehow. I realize it's total paranoia as the straps hold very well, but I wish there was a more "positive" way to mount it so it stays no matter what.
I completely recommend this product.