Dakota's electronic speedometer adjustment unit plugs directly into the stock sockets of 1996 to present models with the electronic driven speedometer. Later models like 2004 to present Sportster, 2006-2017 Dyna and 2007 to present Softail and Touring require hardwiring into stock harness. Speed correction can be made up to Harley's factory margin of error, typically 3-5% of actual speed reading. If correction is made beyond this, it may result in the loss of the 6th gear indicator light and cruise control. This unit allows you to correct the speedometer and odometer reading after a change in tire or pulley size or when a different transmission (different ratio or 6 Speed) has been fitted. Two sealed push-button switches allow the speedometer reading to be increased or decreased easily while the bike is being driven. After you have set the speedometer to the correct reading, the unit stores the correction factor, even with the battery disconnected. The module is completely sealed from water, dust, and dirt. The correction range is from 50% to 200% of the original reading. Small steps allow precise correction to within 1 MPH or 1 KPH.