What is the longest horizontal width of boxed eyewear referred to in the boxing system?

The longest horizontal width of boxed eyewear is referred to as a measurement. In the context of eyewear, this measurement is crucial for ensuring a proper fit and comfort when wearing glasses. It plays a significant role in prescription eyewear, as it relates to how the frames will align with the wearer's face and vision needs.

In eyewear specifications, "measurement" typically indicates the width that spans from one edge of the eyewear frame to the other at its widest point, providing essential data for consumers and opticians alike when selecting frames. This understanding aids in making informed choices about frame styles that are best suited to individual face shapes and sizes.

The other options, such as diagonal, vertical, and overall measurements, describe different aspects or ways to measure eyewear but do not specifically refer to the longest horizontal width. Diagonal measurements would indicate the length spanning from one corner to its opposite, vertical would measure height, and overall could imply a general summary without specifying width. Thus, "a measurement" clearly indicates the precise aspect of boxed eyewear that relates directly to its length in the horizontal plane.