Slide with adjustable slit (frame with glass)

For optical experiments on color decomposition, diffraction and wavelength determination;
Two parts of a black film, one of which is fixed, the second part movable,
This allows different slit widths to be set (no fine adjustment possible), mounted between two glass plates in slide frames
Slit width: 0 ... 2 mm, adjustable
Dimensions: 50 x 50 x 3 mm
Mass: approx. 8 g