The sensors will only detect objects within their preset sensing range and ignore all others outside the range, regardless of the object’s surface reflectivity. Because the QS18FF sensors do not contain any adjustment push buttons, DIP switches or knobs, they are less at risk for tampering or altering. Users simply mount the sensor so that the target will pass within the predefined sensing range and they are ready to begin operating. The QS18FF sensors are priced at $69 each.