I purchased the brown version of this bag for my scooter. I could see using it on any motorcycle rack though. It's very stylish, and I use it daily on my commute. It's pretty big inside, will hold a full face helmet. I use the side pockets for sunglasses and my parking lot pass. I have about 800 city miles on it so far and it's holding up well. I do use a bike cover during the day so it is out of the sun. Overall a great bag and I really like it.
This is my second one of these. When I sold my last scooter, the buyer wouldn't take it without the Prima case. I ride a Vespa ET 4. This case keeps to the classic Vespa styling and keeps my stuff secure and dry. The only reason I didn't give it five stars is that the attachment system is not as secure as I'd like. Other than that: perfect!