Plugs into 96-06 H-D speed sensor harnesses to correct the speedometer and odometer after a change in tire size, pulley size or transmission gearing. Unit plugs directly between the stock transmission sensor and original speedometer; no cutting or splicing required on most models. Two push button switches allow the original speedometer reading to be increased or decreased easily. Can correct speed to within 1 mph from 50% to 280% of the original reading. Sealed completely from water, dust and dirt, the module is easily tucked away into the bike's wiring harness after adjustment is complete. Electric Speedometer Interface Module