When full option, some motorcyclese come with an original top case and if you want to add a carrier on top of that, you can.
The only thing you need is that carrier and four threaded bars which all happen to be part of this package. Ow and you’ll need one of the aforementioned motorbikes as well. With their original top case.
Installing the carrier onto the case is quite idiot-proof. The manual is included but essentially all you do is extend the threaded bars and mount the carrier – and that’s it.