The spec sheet is an important part of the tech pack that shows what the style measures at specific places (called points of measure or POM) in each of the sizes offered. The chart also shows the tolerance for those measurements – meaning the amount plus or minus that the garment can differ from the spec measurement and still be considered acceptable.
An accompanying POM illustration shows where each point is measured on the flat garment. Again, a good tech pack describes details in both words and pictures.
For you as the designer, the spec sheet helps you with quality control for your incoming samples and production runs. Using the chart and the illustration, you can measure your samples to make sure they meet the spec.
The chart can also help you write your product descriptions and provide your customers with detailed fit notes such as the measurements for total length, inseam, or rise so that they order the right size.