Hubs are separated from the cassette by the freewheel body. As a result, the pedals do not always turn and you can easily let your bike roll. With a fixie or single speed (1-speed), however, this is not possible. As there is no freewheel or gear shift on such a bike, the pedals rotate permanently. Freewheel cassette bodies are constantly being developed. Nowadays, some of them have ABG (Anti Bite Guard). This prevents the cassette from rubbing into the hub body. If it is not available ex works, it can be retrofitted for the most common manufacturers by means of a freewheel.