The Wittner Super Mini metronome is among the smallest and most accurate in the world. Measuring 4" high, 1-7/8" wide, 1-1/8" deep. It stores easily in your instruments case and keeps very accurate time. A perfect practice tool for any musician. Comes in a rich ruby mahogany red plastic casing. To use, simple thread the winding key into the right side of the casing and wind it up. Then slide the weight on the pendulum to the mark on the face of the metronome indicating desired tempo, and give it a little push. The arm will swing back and forth making a pleasing “click” sound keeping perfect time at whichever tempo you set. Each winding lasts a very long time! Very very easy to operate.