Same specs, indeed same target, as the 2017a_star, chrome and glass spokes, without the metal slide. It is just the 9 x 5.2 x 1 mm diamond shaped quartz substrate with the pattern.
This is for tight spaces.
Extreme resolution Siemen’s Star. 40 Spoke and Space pairs, from 6.37 cycles per millimeter at the outside circumference to 3,333 cycles per millimeter at the innermost terminus. This corresponds to 150 nanometer spoke or space width at the innermost terminus.
We improved the human readability of the Extreme Star by breaking the spokes with circular spaces at factor of 2 intervals, as the spoke pair period decreases. In order to make the Star even easier to use, at each break we numbered the minimum period with the size in microns . (Except the innermost 2 breaks. The spokes are so small the number features are below the critical dimension of the process). See the SEM images.
Note: an unmounted target is tiny, much harder to use, harder to clean and much easier to lose. Use a mounted target if you can. But sometimes small is what you need so we made this available.