The RPM Shock Duplicator uses a simple comparison method to determine if your shocks are identical. It’s simple, accurate and most importantly, inexpensive! Simply bolt a pair of shocks to the Duplicator and, following the straightforward instructions included, you’ll take all of the guesswork out of your suspension system. No expensive calipers, no “calibrated eyeballs”, just accurate information at your fingertips. All gauge indicator and scale readings are molded directly into the tool for lifelong accuracy.