Auxiliary Objective Lens for applications requiring different resolution, magnification, working distance, field of view and depth of view.
For XTL and XT Series: Objective Outside Diameter 49.5mm, thread Outside Diameter 48mm.
The ring Adapter is for holding the Ring Light, when you use an auxiliary lens, you can fix the ring light on the auxiliary lens. Some times, when you are working with a microscope over heat, steam and particles, you need a ring adapter with a glass