The Beseler 35mm Mixing Chamber for Dual Dichro, and Dual Dichro S Colorheads is used when printing from 35mm format color negatives in either the Beseler 23C or 23CII Series Enlargers.
The mixing chamber doubles the light out put of the lamp head for smaller negatives. They are recommended when working with "slow" printing materials which often require greater then normal light intensity or an unusually long printing time.