The Taktell Supermini Metronome uses the same mechanics as the Piccolo Pocket Metronome and the standard Wittner metronomes, but in a smaller plastic case. Even with the smaller size, the metronome is very accurate, with the speed being set by the adjustable counterweight. The key can be kept on the front plate under the cover so it doesn't get lost.
 
Stock photo of product. 
 
UPC: 4008687884001