The Aven Tools Aven Tools SPZHT-135 Trinocular Stereo Zoom Microscope is the ideal scope for a wide range of investigative and inspection applications. The SPZHT-135 extends the boundaries of stereo zoom microscopy, employing standard 15X eyepieces to achieve 21x to 135x continuous zoom magnification, all the while providing a continuous working distance of 3.3 in. (84 mm). Graduations on the zoom knob indicate to operators the exact magnifications at which they are working; this is particularly helpful for applications requiring very specific adjustments. Replacing the standard 15X eyepieces with optional DHW20X eyepieces enhances the magnification range of this dynamic microscope from 28x to 180x. Having eyepieces set at a 45 degree angle, the adjustable interpupillary distance between eyepieces of 1.96 to 2.91 in. means they can be set to the comfort level of any user.