In the boxing system, the horizontal measurement of a lens is referred to as the:

In the boxing system used in eyewear terminology, the horizontal measurement of a lens is referred to as the "A box." This measurement represents the width of the lens itself and is crucial for determining how the lens will fit within the frame. Accurate measurement of the A box helps ensure that the lenses are properly centered in relation to the pupil and that they provide optimal optical performance.

Understanding the boxing system is important for any optical professional, as it aids in creating lenses that fit frames perfectly while also considering aspects such as lens height and curvature. The A box measurement is typically taken at the widest point of the lens, contributing to the overall aesthetic and functional design of the eyewear. This terminology is standardized, allowing for consistent communication and understanding within the optical field.