This is very affordable, unmounted, 1 inch (25.4mm) diameter optical slit, made of aluminium (0.2mm, 0.1mm thickness) or stainless steel (0.05mm thickness).
The front side is marked with slit length and width, the back side is left blank. The thin middle line marked on the front side helps with the alignment.
Stainless steel slits have no marking on either side to reduce thermal deformation of the thin material.
Length: 3mm
Width: 50um
Width tolerance: +0/-5um
Thickness: 0.2mm (standard) or 0.1mm (special) or 0.05mm (special)
The 0.1mm version is a 0.2mm thick substrate which is thinned out in the middle area by laser etching.
Great for DIY spectrometers, slit-scan imaging, image- and laser beam sampling or other optical experiments.