Baader Barlow Lens 2.25x/1.3x Q 1.25"

Product description:

A Barlow lens lets you increase the focal length of your telescope and hence the magnification. The Barlow lens is placed between the telescope and the eyepiece.

How the Q-Barlow lens works - Screw the lens element into the barrel of the Barlow and you get 2.25 × the focal length. Alternatively, the lens element can be screwed directly into the filter thread of an eyepiece. This results in increasing the magnification by a factor of 1.3.