I have a 23C with a 23dga dichro head. I recently picked up a 35mm Light Concentrator for dga heads (Beseler #8199), consisting of a diffuser mixing chamber (with reduced diameter diffuser plates) and a 1 3/4" x 1 3/4" x 6" high metal tube. The purpose is to concentrate the light when using 35mm negatives to reduce print exposure time. Since it didn't come with instructions, where does the metal tube go and how is it installed?