Abstract: The present invention broadly comprises a device, such as a slider, for performing phase contrast microscopy, the device containing a plurality of at least three phase contrast annuli. The slider is received into a microscope condenser mounted under a microscope stage and that is adapted to receive the device and align the device such that a phase contrast annulus is aligned with an appropriate microscope objective phase ring. The invention also comprises printed or engraved indicators or other markings indicating whether the bright field aperture or a particular phase contrast annulus is in position in the illumination path of the microscope. The invention further comprises a device for preventing the removal of the device from the condenser.