The Expander Optics 10X refers to a type of optical beam expander. Specifically, the 10X HeNe Fixed Beam Expander, identified by stock number 55-578, is designed for expanding and collimating laser beams. It features a fixed magnification of 10X, meaning it can increase the diameter of an incoming beam by ten times. The device has a broad-band anti-reflection coating effective in the 450-750 nm range, suitable for visible light applications, particularly in the red spectrum around 633 nm (design wavelength).

The beam expander has an entrance aperture of 2 mm and an exit aperture of 27 mm, with a focus range from 1.2 meters to infinity. This implies that it can handle beams with a diameter up to 1 mm while maintaining less than a quarter wavelength of wavefront distortion at the design wavelength. The device weighs 458 grams, has a housing diameter of 50 mm, and a length of 118 mm. It is designed with C-Mount threading for compatibility with various optical systems and maintains beam divergence adjustments through a non-rotating mechanism.

These devices are typically used in applications that require precise beam shaping and expansion, such as in laser engraving, material processing, and various scientific research applications. The choice between them would depend on the specific wavelength and beam size requirements of the application.