Using a LED readout and sound, this solid state device measures the change of inductance in the magneto coil when the points open or close, allowing you to properly adjust and synchronize the timing on all breaker point type magnetos. 4 ft leads and instructions included. Size of anodized aluminum case: 3/4″ x 3″ x 5″. Weight: 9oz. Uses one 9-volt battery, not included.