Keeping Auto Car Truck Boat Marine Steering Wheel Knob Spinner Handle Power Ball Impact Resistant Plastic Knob + Stainless Steel Metal Clamp Diameter of shift knob: approx 5.5cm When turning car, it lessens the turning radius thus helps beginners and lady drivers to drive safely and conveniently Suitable for the steering wheel diameter below 32 mm Can be applied to car & boat & marine steering wheel