The OTTO Tuning System is a vision App and hardware kit that enables you to conveniently check and adjust your bicycle with professional precision. This App requires the purchase of OTTO Gauges from OTTO DesignWorks or an authorized dealer. The OTTO App offers progressive levels of adjustment with both CHECK and TUNE functionality. CHECK allows cyclists to confirm the accuracy of their bike's shifting and whether additional adjustments are needed. TUNE gives cyclists the option of a simple barrel nut-only adjustment or complete tune, which includes adjustments to the high and low limit screws, and cable tension. The OTTO App also provides multiple bike profile capability. Features & Benefits of the OTTO Tuning System: ● Convenient - Do-It-Yourself. Make adjustments on your schedule. ● Easy to Use - Interactive screen graphics and clear audio instructions. ● Fast - CHECK confirms your tune quality in under 30 seconds. ● Complete - TUNE provides barrel nut adjustments in under a minute and complete limit screw verification and adjustment in less than 10 minutes. *requires In-App purchase* ● Precise - Ensures shifting accuracy to +/- 0.125 mm (0.005 inches), less than 1/8 barrel nut turn.