You have 8 meeting your criteria.
The step circular neutral density filter can be used for calibration of illumination systems. The Step CND filter is useable from 370nm to 2600nm. The step circular ND filter configuration consists of a circular glass substrate with spectrally flat neutral density metallic coating on one surface. The density variation takes place in discrete steps around the filter. The step circular neutral desnity filter can be supplied in any configuration and other density steps upon 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
Flatness: < 2 Fringes / Inch @ 632.8nm
