Amazon.com: Neewer 6 Pieces Guitar Machine Heads Knobs Guitar String Tuning Pegs Machine Head Tuners for Electric or Acoustic Guitar (3 for Left + 3 for Right) : Musical Instruments
TronicalTune: A robot tuner for almost any guitar (hands-on) - CNET
Amazon.com: Neewer 6 Pieces Guitar Machine Heads Knobs Guitar String Tuning Pegs Machine Head Tuners for Electric or Acoustic Guitar (3 for Left + 3 for Right) : Musical Instruments
Kluson 6-In-Line Diecast 2-Pin Tuners for Fender Guitars - StewMac