Some scopes will be specified as 4X32, for example. The 4X is a fixed magnification – 4 times larger than with the naked eye. The 32 is the size of the objective lens (the one at the far end from you) in millimeters. In general, larger objective lenses capture more light, providing a clearer image.Many modern scopes have numbers like 3-9X40. These have variable magnification, between 3X normal and 9X normal. As you go up the scale, the field of view (FOV) is reduced. As with fixed magnification scopes, the 40 indicates objective lens size.