Olympus Darfield Condenser specifically for the Olympus CHA, CHB, CH2, and original hamertone grey BH. To my knowledge it will not fit any other microscope series. The condenser installs from below the fork on these microscopes and is secured by the mounting screw. These condensers are new but not in original packaging.  It is a simple matter to install, just remove the old brightfield condenser and replace it with this one. It takes about 30 seconds and can be switched back and forth between the two.  Thanks for looking!