How much do you want to spend?
Is name brand important to you?
I was on a budget, when I bought mine. $75!
Bestem TBox. It's actually a Givi knockoff. I've seen the Givi beside mine, and it's almost identical!
For a while, I used the mounting plate that comes with it (included in the price, btw... not additional cost like a Givi), but tired of how the plate looked on the rack w/o the trunk.
So, after discussing it with Phillip in Texas, and after purchasing one of his beautiful racks, I took some measurements of mine, drew it out and sent it to him. We concluded that the pin/latch locations were slightly differently located than the Givi, and that the latch is actually backwards facing from the Givi's. He sells an SWMotul kit for his racks. I simply turned the latch post around, relocated it rearward just a bit, added some extra felt pads to the bottom of the trunk for spacers, and presto!
It's worked perfectly for 2 years now! No problems, and looks great when not using the trunk.
Bestem makes a liner for the TBox, too. I also got a bit creative, and cut in some extra LED strip lights in the red band portion. It already comes with an LED built in, so I wired mine so that I can have the 2 I added as running lights, and the factory's as a brake. Looks great, works great, increases rear visibility.
Bang for the buck, I love this trunk. It works.
I will say this, though... If you want a huge one, large enough for 2 fulfaced helmets, this one's slightly too small. One helmet, and lots of other stuff fit fine, though. I think it's considered a 42 litre size, IIRC.
Just a suggestion for another option... for those like me on a budget.
