System 250 Microscopes - Binocular Stereo-Zoom Microscopes with sturdy, heavy duty, cast aluminum alloy housing that rotates 360° in its focus mount. Models are standard with 10X widefield eyepieces and have a zoom range from 6.5X to 4.5X giving them a magnification range of 6.5X - 45X. The zoom control is by graduated knobs on the sides of the body. The extended magnfiicaion range is from 3.25X to 225X when using optional eyepieces and accessory lenses.