This is a Nikon-made lens that has auto focus to give you the best setting for each picture. The filter size is 52 mm, good to know if you like to use filters.
From London Camera Exchange
Nikon 800mm f/5.6E FL ED VR AF-S NIKKOR
Clifton Cameras
Nikon 800mm f5.6E FL ED VR AF-S NIKKOR Lens