This is an unmounted, precision optical pinhole, laser cut in an aluminium metal shim. The thickness of the metal shim is 0.2mm but it can be thinned by laser etching to about 100um thickness using laser etching before cutting the hole.
For pinhole photography purposes the thinner version is more useful. (A 100um hole on a 200um substrate would limit the numerical aperture and internal reflections/scattering would cause various image quality issues.)
The aluminium substrate is as default 1 inch / 25.4 diameter, circular shape. Other sizes and shapes up to 2inch diameter or 2inch x 2inch rectangle are possible. Please contact me at firstname.lastname@example.org if you want a custom size at no extra cost.
Great for spectrometers, quasi-coherent light sources, spatial Fourier filters or other optics projects.