Our left eye and right eye can be different in their vision and focusing capability. Therefore, to use binoculars properly, we must compensate for such a difference, and centre-focusing binoculars have an adjustment mechanism to achieve this. You can find that almost all the binoculars listed in our store have one eyepiece (usually the one on the right-hand side) which is independently adjustable with a marked scale.
To adjust binoculars, first, use a lens cover or your hand to cover the right objective lens which is on the same side as the adjustable eyepiece (note: better to keep both eyes open to avoid distortion by squinting). Look through the binoculars and use the central focusing mechanism to focus on a distant object until it is sharp and clear.
Second, transfer the lens cover to the other lens on the left, again with both eyes open, but this time adjust the focus on the same object using the adjustable eyepiece only, until it is clear. Your binoculars are now properly focused for your use. Adjust the distance between the two eyepieces so that they in the centres of your eyes (i.e., when the two cycles merge into one). You can now use the central focusing mechanism to focus on objects at different distances, but you should keep the adjustable eyepiece at the same focus setting unless it is accidentally moved or the binoculars have been used by someone else.