There are two popular sizes of microscope viewing lens barrels: 23mm and 30mm. The Xtend-a-Scope 37M kit comes with two interchangeable tubes to handle both types. It's very simple to remove one tube and screw in the other. The Xtend-a-Scope 37M is built around a high quality optical 10x eyepiece, so you simply remove your existing eyepiece and insert the Xtend-a-Scope 37M. Focusing can be accomplished through the use of the LCD screen.

Because the lenses on many digital cameras are not removable, you need to use a type of microscopy that's called "afocal." It simply means that you use the viewing lens of the microscope with the lens of the camera. Most people set up the microscope, then use a tripod to adjust the lens of the camera to point directly into the viewing lens of the scope. While this does work, it's difficult to maintain the proper viewing angle while keeping the lens of the camera as close as possible to the viewing lens of the microscope, otherwise you get a vignetting effect (i.e. the picture doesn't fill the entire frame, and it appears like a tunnel, surrounded by black).

To eliminate this problem, you can use the Xtend-a-Scope 37M to connect your camera directly to the microscope. The Xtend-a-Scope 37M can also be used to connect a standard 35mm camera to a microscope using an appropriate thread reduction adapter to change the thread size.