Reference with Cp-2 1/3 to the white mark of base plate showing to end of rail or back of camera body:
NN3, length of upper rail 130mm, URS max 117mm
NN4, " 160mm, URS max 139mm
NN5, " 170mm, URS max 149mm
This will help you to make your choice for the right NN Product for your camera lens combination for NN3 NN4 panohead.