The 1.7x magnification extender increases the magnification by a factor of 1.7. You can quickly and easily attach it using the bayonet catch to all the objective and eyepiece modules in the ATX / STX / BTX family. In the case of the BTX 65 and 85, the magnification increases from 30x to 50x, and from 35x to 60x for the BTX 95 and 115.