The 20XR objective lens can replace any of the lenses in the lens cluster of the Sonlight Ultra microscope.
The Sonlight Ultra microscope comes equipped with a lens cluster that contains three objective lenses: 4X, 10X, and 40XR. In laymen's terms, that means each of the three lenses magnifies 40, 100, and 400 times what they're viewing. (The "R" means the lens is retractable to prevent scratching.)
You can remove any of the lenses in the lens cluster by unscrewing it from its threaded socket. You can then add in its place an objective lens with a different magnification should you desire to do so.
That's why we sell the 20XR (200x magnification) objective lens.