The Superlift TruSpeed was the unit actually recommended to us by three of the four local Jeep dealerships we contacted regarding TJ speedo recalibration. The TruSpeed features two settings just in case you run two different tire sizes on the same vehicle. Just toggle between setting A and B. The unit wires into the factory electronic speedo plug and taps into the factory fuse box for its power supply. Installation is straightforward, and the instruction booklet is very detailed.