The objective lens dimension is the second selection within a binoculars description. A 10X42 binoculars ensures that the target lens diameter is 42 mm. Here is the lens to the front from the binoculars. Your selection of magnification will depend upon how far you’ll really need to use the binoculars. https://techonpage.com/story3402547/not-known-facts-about-hunting-supplies-uk