What is a "spec"? A spec is a "size specification"or a measurement on a garment. There are many measurements on a garment that indicate to a pattern maker how to make a garment. A list of these measurements is called a "spec sheet". A spec sheet is a key page in a "tech pack" or "technical package". A company will usually set standard "specs" as a guideline for a size to ensure consistency in fit. Once these standards are set, measurements are "graded" down (to say a size 2) and up (to say a size 16). Standard specs are usually determined by 1) the fit model chosen for a brand 2) market research on the fit of the competition and 3) customer feedback.