Two gear belts are included, so I have one gear on the zoom ring and one gear on the focus ring. I use it with a Nikon 70mm 300mm lens and it has no trouble focusing or zooming smoothly. The only problem I have is that if you install it with the Zhiyun TransMount Image Transmission HD Video Transmitter 2.0, you won't be able to balance your Weebill S if it's too heavy and your Weebill S in front becomes too heavy. Otherwise it works great!