The present invention relates to a brush unit (3) and to an associated rotary brush tool. The brush unit (3) is equipped with a brush holder (10, 11), which can be driven in rotation, and with an annular brush (4, 5) with a bristle-covered rim (8) with outwardly protruding bristles (5). Furthermore, a stop means (14) which dips into the rotating bristle-covered rim (8) is provided. According to the invention, the stop means (14) simultaneously acts as an abrasive body (14) for the bristles (5). In this case, a distinction is made between both functions (stopper function and abrasive function) according to a direction of rotation (R) of the annular brush (4, 5) and/or a setting position of the stop means (14) as compared to the bristle-covered rim (8).