Abstract: Embodiments of this disclosure comprise of an optical cube, a light source, a cube holder connection point, a plurality of pins, a plurality of cavities sized and configured to receive said pins, a magnet, and a magnetic element located to attract and adhere to said magnet. An optical device with coaxial illumination for reflected light and fluorescence detection includes one or more optical cubes to redirect light along the optical axis. The cube holder connection point can be in a fixed position, moved translationally, or moved rotationally to engage a cube within the optical device. An optical cube can be attached to the cube holder connection point utilizing locating pins and magnetic coupling to constrain all 6 degrees of freedom. Use of such devices reduces the need to use screws or other locking hardware and permits a larger number of optical cubes to be inserted in the same area and makes it easier to exchange optical cubes.