You have 5 meeting your criteria.
The step linear neutral density filter (ND Filter) can be used for calibration of various illumination systems. The ND filter can be used from 370nm to 2600nm. The step linear ND filter configuration consists of a glass substrate with a spectrally flat neutral density metallic coating. The density variations take place in discrete steps. Step linear neutral density filters are supplied with calibration data. Other configurations and custom step linear ND filters are available on special order.
Reynard Corporation standard parameters apply:
Substrate Material: BK-7
Thickness: 2mm +/- 0.2mm
Surface Quality: 80-50 Scratch & Dig
Parallelism: < 3 Arc Minutes
