Three teaching aids devised by Wolfgang H Berger to accompany teaching model, inventory number 1993-421/2. Each is comprised of a long metal rod with hollow metal tubes fixed in different positions, through which a light is shone to project a diffraction pattern. Used to demonstrate how beam spreads and the need to focus it with the mirrors. One of these models is now broken.

From a collection relating to the X-ray crystallography research carried out by Dame Kathleen Lonsdale at University College London.