2M on the box means the cable length of the sensor, not detection range. 

manual not updated and 4m on the manual is not correct.

Retro-reflective sensor for gate opener, boom barrier;

for the power supply, there are 110V/220V version and 12V/24VDC version;

when installing it, make sure no sunshine interferece; 

--  Light resource: Infrared LED 

--  Strong anti-shock and anti-vibration. 

--  Non-contact object detect: Avoid the photoelectric sensor to contact the object directly, protect the inducing component from damage and extend the operation life of the sensor. 

--  Detect any objects with different materials: Detect objects by the light quantities reflected and received, detect objects such as glass, metal, plastic, wood, fluid...etc. 

--   Fast response: Max. 3ms 

--  Identify object colors: According to the colors' reflectivity and absorptivity, the sensors detect the light that the object reflected and identify the colors. 

--  High precision: Precise electron circuit, can detect tiny objects with accurate position.