Nikon F4s (left) and F4 (right). The difference between the two is the battery grip. The grips are interchangeable between the bodies which are identical. The F4 came with the smaller MB20 that holds 4 AA's and was not sold in the U.S. The F4s was sold in the U.S. and came with the larger MB21 grip holding 6 AA's allowing for continuous shooting at about 6 frames per second and having a vertical shutter release.