This aluminum needle-based electroscope’s design makes it superior to traditional leaf-style electroscopes in part because the needle stays put when experiments are being performed, versus 'old' electroscopes where the leaves ‘flutter.' The ultra-sensitive needle pivots on an axle when an electric charge is applied to the disk located at the top of the electroscope. Includes charging ball, condenser plates, and an insulated rod. 2.4 x 3.7 x 4.1 in. (60 x 95 x 105mm). Ring diameter 150mm.