In this category there are the Nexave and Nexus Shimano Roller Brakes. These roller brakes are designed for use with Nexave and Nexus hubs, where the brake mounts directly and neatly on to the hub.
There's no need for external callipers or cantilevers. The braking mechanism is sealed away from the elements - braking performance stays the same whatever the conditions. A variety of models are available in different sizes.