This is a description taken from LEGO.com. Do not modify it.
Infrared Seeker power for your LEGO® MINDSTORMS® NXT robots!
Upgrade your LEGO® MINDSTORMS® NXT creations with the Infrared Seeker sensor! Your robots will be able to detect infrared light sources and determine their direction and relative strength thanks to 5 infrared detectors arrayed at 60º intervals.
Includes 1 Infrared Seeker.
Does not include connector cable.
This is the individual component, and does not include the NXT Intelligent Brick, software or any accessories. It requires the complete LEGO MINDSTORMS NXT set (#8527 or #8547) for use.