MICROSCOPE EYE PIECE

The eyepiece sits at the top of the body tube, above the

objective lenses and revolving nosepiece, and is often removable for swapping magnification powers like 10x, 15x, or 20x.
It typically houses one or more lenses in a cylindrical tube, with designs like negative (internal diaphragm) or positive (diaphragm below lenses) to correct aberrations and define the field of view.