Car’s wheel hub assembly bk21-2B664-DB includes the wheel speed sensor that controls your anti-lock braking system(ABS). The sensor keeps sending a constant signal to the ABS control system, telling it how fast each wheel is running. In an emergency situation, the ABS control system will determine if anti-lock braking is required. If the ABS sensor doesn’t work properly or fails, the ABS system fails, so the quality of this sensor(how it is made and protected from damage) is critical to braking safety, hub bearings from Hangzhou Liyi Bearing Co.,Ltd are all adopted high-quality sensors, which ensures the wheel bearing running smoothly.