Feature This tool allows you to find the appropriate offset / wheel size, showing you how the outside edge of the wheel will fit with the fender. Simply attach the base to your wheel hub (will fit ANY 4 or 5 lug bolt pattern). Set the wheel height, width, and offset and the red line on the tool will show you exactly where your outer lip will sit. This tool can simulate all sizes below. - Wheels from 13 inches to 20 inches - Wheel width from 7 inches to 13 inches - Wheel offset from -40mm to +40mm - Compatible with all 4 and 5 lug hubs Note: 1. For best results in seeing how a wheel will fit when your suspension is preloaded. Before jacking up your car, measure the distance between the ground and your lower control arm. Then, after jacking up your car, taking the wheel off, attaching the tool, and setting your sizes. Lower the car back down but with some wood under that hub until the lower control arm is at the same height as the car sat previously. This will show you where the outer lip of a wheel would sit in relation to the fender when the car is at ride height. 2. Please take into account things such as inner wheel well clearance with the tires, brake rotor and caliper clearance, suspension clearance, etc. Wheel diameter is measured by wheel face where the tire seats on the wheel, not including the outer lip. Wheel width is measured by the width between the inside of the wheel lips that retain the tire. The outside location of the lip can be varied by the height and thickness of the lip.