The dual dichro assembly is a bit confusing, since it lets you use the dichro head with either the condensers that came with the 23C or as a diffusion head. I found I still had the box for mine, and I dug it out and discovered that I also still had the instructions. The first thing I noticed is that the dichro lamphouse will not clear the condenser stage adjustment knob. The original kit has an extension for the shaft. The dichro lamphouse is a good deal heavier than the original, so the original counterbalance spring is inadequate for it. The original kit also has another spring and bracket to take care of that problem. These parts may still be available from Beseler. The dichro lamphouse mounts to the body of the enlarger with brackets and screw knobs that are also included in the kit. As you can see, there is a quite a bit more to setting up the dual dichro head than just setting it onto the enlarger. To mount the head, you first need to remove the current lamp assembly. The dual dichro kit comes with two different diffusers for either condenser or diffusion illumination. I have mine set up for diffusion. To do that, you remove the condensers and put in the diffusion diffuser (which goes in the lower slot of the filter drawer). You then mount the dichro head and lower the condenser stage to the 2X3 position. To set the system up for condense illumination, you keep the condenser in place and mount the conic light integrator into the dual dichro head; then you mount the dual dichro head. The whole thing is non-trivial, and it does not work without the right parts.