The RZ-B is the central component of any RZ system. The zoom optics have a 10:1 zoom ratio and a base magnification of 0.75x to 7.5x. Depending on your selection of eyepieces and objectives, this translates into an total magnification range of 3.75x to 300x. The zoom controls indicate magnification at 12 positive click-stops throughout the zoom range, making photograph framing and measuring easily repeatable and consistent. Dual-iris diaphragms offer excellent control over resolution, contrast, and depth of field. The zoom optics are housed in a rugged aluminum alloy body for increased stability and durability, and all components are coated with an anti-static finish to protect sensitive specimens.