The Judy Discovery Digital Clock features a classic yellow design with visible green and red working gears * Simply turn the large knob on the back of the clock and watch the gears at work, moving the big red hands on the clock face in unison with the digital clock numbers * The synchronized digital clock, with its movable window below the analog clock, provides the perfect self-check for children who are just learning to read analog clocks * Clock is designed for children in kindergarten to third-grade (ages 5 to 8).