A slip ring can be made in different ways and with different materials.
The important thing with rings is to make them as small as possible. The reason for having a small slip ring diameter is to keep both the voltage drop and friction down (minor losses to cool off). It is always better to make the rings wider than to go up in diameter to create an effective area.
Stainless steel rings are more resistant to mechanical wear, but at the same time not as good a conductor. It is therefore important to make a choice between bronze or steel rings from the outset.
For more information see our data leaflets in pdf-format.