The Beseler Dual Dichro Colorheads are configurable to provide either condenser of diffusion illumination. In condenser mode, it uses the normal set of condensers provided with the Beseler 23C condenser enlarger. For diffusion illumination the condenser set is swapped out for this diffusion module. This item was sold with the Dual Dichro & Dual Dichro S lamphouses, full installation and use instructions are provided in the Beseler instruction manual. These modules are used, but are in perfect working condition.