The Graph Tech Tune-a-Lele Ukulele tuners are super light machine heads with a uke-friendly 6:1 gear ratio. This super light, yet strong machine head makes ukuleles balanced, not Headstock heavy, and makes tuning so much easier. The Graph Tech PRU-5004 is a set of RATIO Machine Heads for ukuleles that use 4 tuners. This set has larger buttons than other versions. These Graph Tech ukulele machine heads are a perfect fit for all types of ukuleles, except Sopranos.