AmScope FT-B45 Microscope Blue Light 45mm Filter

Dimension: 45mm (1-3/4") in diameter approximately.

A typical use would be a blue filter when using low levels of light in a brightfield application. (Like dry layer blood analysis.) When low levels of light are used, you usually get a yellowing effect because the lamp is turned low. The blue filter brings the light back to a more natural white light.