The first number with the "X" behind it, is the power (ie. 8 & 1/2 power or 10 power)

8 & 1/2 times or 10 times normal human vision.


The next number is the diameter of the "front" lens (ie 42MM = 42 milliameters).

The larger the "front" lens the better the light gathering ability.

However, the bigger it is, the more weight; as a rule.


Warranty ?? - It's lifetime !