Emporio Rossi sells drum brakes of the following brands:
The drum is made up of a rotating cylinder, rigidly joined with the braking shoe. The rotation of the drum is stopped by the brake linings, made of a material that creates friction when pushed towards the internal side of the drum by the brake shoes.
As time passes by, and miles rack up on the odometer, brake linings wear down and they have to be replaced periodically. The drum tends to wear down internally as well, and , in order to avoid replacing it, it is possible to carry on rebores to make its circumference regular again. This operation has the natural consequence of a light increase in the internal drum diameter. The rebore can be carried out until a certain diameter, decided by law, and that varies depending on the single drum brake.
After a rebore, it is also necessary to mount a bigger brake linings set, because the diameter of the drum brake has been altered by the rebore operation.
Drum brakes are common especially among trailers, and a bit less among road tractors, where manifacturers tend to prefer the caliper-disc-pad system.