Otto Tuning System 10, 11 Speed Cassette Includes a cassette gauge that is compatible with 10 and 11 speed cassettes, a derailleur gauge, and a small Quick start guide Easy to use - interactive screen graphics and audio Instructions Fast - Quick Tune & full Tune modes; complete adjustments in 1 to 5 minutes Precise - shifting accuracy +/- 0.125 mm (0.005 inches), which is less than 1/8 barrel nut turn For Select Shimano/SRAM derailleurs. Only Available for iPhone 5, 5C, 5S, 6, and 6+ running Ios7 or Ios8