The new M2 Sensor is 40% more light sensitive. This allows recoding of velocities in lower light conditions that the original Millennium Sensor. Packaged individually, each sensor comes with 20 ft. shielded cable attached. The M2 Sensor is designed specifically for the CED M2 Chronograph system, but will function with the original CED Millennium Chronograph. It is IMPORTANT to note that the original sensor and the new M2 sensor should NOT be mixed in use. Both MUST be paired with the same type.