Double the magnification of any eyepiece. Simply insert the eyepiece into the 2x Barlow, and get an instant power boost.

The focal length of the eyepiece is divided by 2, so a 25mm eyepiece becomes 12.5mm. The field of view is also halved.

Many astronomers prefer using lower-powered eyepieces with a Barlow to higher-powered eyepieces, due to being more comfortable to work with.