Componon-S 5,6/210 Flange or Ring?

I want to mount this lens onto a Zone VI mod 2 enlarger lensboard. Century Optics/Schneider USA only supplies a mounting flange, and does not stock a retaining ring.

Why is a mounting flange superior to a retaining ring, or should I just keep looking for a M55x0.75 retaining ring?

Thanks,

Tim

Go to SK Grimes and get them to supply you with what you want. They are real pros.