The box system dimension seldom used anymore is which measurement?

• A. A Measurement
• B. B Measurement
• C. C Measurement
• D. Dbl

Answer: (C)

The box system uses a set of dimensions that describe the imaginary box around the lens, essentially outlining the size and fit of the frame. In modern practice, the most relevant measurements are the vertical and horizontal box sizes (often called A and B) and the distance between the lenses across the bridge (DBL). The third box dimension was used historically, but it isn’t needed for most frames or for processing lenses today. Because it rarely affects fit, manufacturing, or ordering in current workflows, this particular dimension has fallen out of common use. Therefore, the measurement that is seldom used is the third box dimension.