In the boxing system, the vertical measurement of a lens is known as the:

The vertical measurement of a lens in the boxing system is referred to as the B box. This measurement represents the height of the lens shape, which is essential for ensuring that the lenses fit properly within the frames of glasses. The B box measurement helps in fitting the lens to the wearer’s needs and preferences, specifically concerning the vertical alignment of the eyes to the optical center of the lenses.

In contrast, the A box measurement refers to the horizontal width of the lens shape, while the C and D boxes do not correlate with standard lens measurements in the boxing system. Understanding these distinctions is crucial for accurate lens fabrication and frame fitting.