Generally, a bicycle head tube and headset size are about a 1-inch diameter steer tube: some manufacturers are not also offering 1⅛ inch diameter of the steering tube. They are sufficient for regular bike rides on roads. But if you are looking for added stiffness to the steering portion of your bike, as in the case of mountain or racing bikes, you will need a larger diameter. So, an ideal option depends on the type of bike and your cycling style. It is great to do some research and brainstorm before buying a new headset.