An enormous 53 litre top case that's big enough to hold two full face helmets, or a weeks worth of clothes along with anything else you can think of carrying on your trip (unless you're taking a female, in which case you'll never have enough space). Might make filtering through the rush hour traffic a little tricky, due to its width, but if you're loaded up to the gunnels then it's a lot less hassle than a backpack and far less intrusive than a tank bag. Gives a pillion something solid to rest against too. It's tough, unclips easily from the base plate and is more waterproof than a bungeed on shopping bag. What's not to like?