The picture you posted shows the enlarger with the flat lens mount (421-100) attached. That mount will accommodate lenses from 50mm up to 105mm with the appropriate lens disc. I have a 39mm threaded lens disc which makes lens changes very easy (eliminates the need for multiple discs and retaining rings). You will need the 2 3/4" cone (421-101) for a 135mm lens and the 4 1/2" cone (421-102) if you use a 150mm lens.