Ernie Ball Power Peg Pro is the latest edition to the motorized pegwinder family. Featuring a newly engineered wider head that fits all electric, bass and acoustic guitar tuning machines. Restring instrument up to 80% faster than manual peg winders. The Power Peg Pro is equipped with more torque working with all tension requirements from mandolins to ukuleles to vintage basses. With rechargeable lithium-ion battery and power adaptor (included), buying batteries is now a thing of the past.