We use these small cars in conjunction with GoPro Action Cams. The processing of the product is fine, it smells a little of oil or fat, but that was the time already much better. What I have noticed something negative: the running noise of the roles are quite noisy and therefore good to hear on the video.
For us, this is no longer relevant, but perhaps for people who need the sound of the camera also. But perhaps it also helps already to oil the ball bearings, or hanging replace if required.