Harley-Davidson risers are typically measured in terms of their rise and center-to-center measurement. The rise refers to the vertical distance between the base of the riser and the center of the handlebar mounting hole. The center-to-center measurement indicates the distance between the two mounting holes on the riser.
For example, a common measurement for Harley-Davidson risers might be "4-inch rise, 3.5-inch center-to-center." This means that the riser has a vertical rise of 4 inches from its base to the center of the handlebar mounting hole, and the distance between the two mounting holes on the riser is 3.5 inches.
It's important to note that riser measurements may vary depending on the specific model and design of the riser, so it's always recommended to refer to the manufacturer's specifications or consult a Harley-Davidson dealer or expert for accurate measurements for a particular riser model.