23C and early 23CII enlargers were equipped with a sliding filter tray for the red safety filter. They were never supplied with an under-the-lens type holder. Most owners aren't aware that a proper under-the-lens holder is a simple retrofit - the mounting holes are already there! This kit includes the filter holder, mounting bracket and mounting hardware. The kit can also be used to replace a missing filter holder on later 23CII, 23CIII-XL and 45MX II enlargers.