Reference dimensions are supplementary measurements provided on an engineering drawing to clarify the size or location of features, but they are not intended to control manufacturing or inspection processes. These dimensions are enclosed in parentheses and serve only as informational aids, often derived from other basic dimensions that already control the design. Since reference dimensions can lead to redundancy or confusion, best practices recommend minimizing their use to maintain clarity and focus on the critical dimensions that directly impact manufacturing, assembly, and quality control.
