Omega #421-903 lens plate with 1/2" cup and 50mm hole for mounting certain enlarging lenses with 50mm mounting thread on the #421-900 Single Lens Mount for D5500 and ProLab II enlargers. For specific applications for this lens plate, please refer to our D5500 / ProLab II Lens Mount Reference Chart.
Note: These lensboards are not threaded - a 50mm retaining ring is required to mount the lens.