I have a Givi Tank Lock XS308. I'd buy it again.
Got rid of the dumbass, useless map holder on top, as well as the forward shoulder strap (cut it off). Now it's perfect. Holds *lots* of gear, that you want to access quickly, is not intuitively easy to pull off the bike by someone not familiar with it (but takes 2 nanoseconds to unlock it, and even less time to pop it back on securely).
I rode 3-1/2 hours back from the Dragon last year, in a whipping downpour the entire way, and the rain cover didn't budge, and the tank bag remained bone dry.
The bag (at first) appears large, if you're not used to it... however, I've been riding with it a *long* time, and it couldn't imagine not having it... Just too convenient.
2015 Versys 650 Pearl White
[space holder for farkles...]