The darkfield condenser allows you to render detail in specimens that would otherwise be transparent. Using principles of light-diffraction to suppress field-illumination, the condenser illuminates edges of cells, microorganisms, and other objects. This is particularly useful for live blood analysis. This is a darkfield condenser designed for dry use with lower magnifications. The 0.9 maximum numerical aperture will accommodate lower-magnification objective lenses with numerical apertures up to 0.9. However, it is recommended to use objective lenses with numeical apertures below 0.7 for true darkfield. For magnifications above 40X, it is recommended to use the oil condenser. The condenser has two centering screws for properly aligning the illumination halo. This allows you to optimize the lighting on microscopes that do not have centerable condenser-holders. This condenser is designed to work with compound microscopes with a 37mm bottom-mount condenser holder. Compatible models include: B340, T340, B400, T400, B450, T450, B460, B490, T490, B590, T590, B600, T600, B680, T680, M220, M600 Condenser Mount: 37mm bottom mount Model Compatibility: B340, T340, B400, T400, B450, T450, B460, B490, T490, B590, T590, B600, T600, B680, T680, M220, M600 Numerical Aperture: 0.7-0.9 Immersion Medium: no Centerable Optics: yes