Very high-quality top case for its price... it fits an XL helmet (pilot Hermes jet) and some small items as well. Very easy to install, even on the rack of the Daytona sprinter (by drilling 2 holes). It can be easily removed and reattached with the push of a button and used as a "suitcase." The only negatives for me are that the lid makes a bit of noise on rough roads (I have stuck carpet inside) and that it necessarily requires a key to close. But for its price, I simply overlook these.

This specific top case rattles like there's no tomorrow... Even at idle, with my scooter being only 125cc, you can hear the plastics banging against each other. Of course, it also happens with the slightest imperfection in the road.
In terms of capacity, a full face helmet (specifically HJC RPHA 11) fits very tightly and diagonally; it needs to be placed carefully to avoid rubbing on the sides. Inevitably, it will happen at some point and it will leave marks. The 30 liters could be distributed a bit better.
Finally, regarding the installation, it's a bit of a hassle to do it by yourself; it requires various tools, a screwdriver, a wrench, a ratchet to hold against, etc.

Very beautiful and very good construction. Fully usable space that fits a helmet and various small items, such as a raincoat, gloves, etc