Professional sourcing requires a deep dive into material specs. You should request details on fabric weight (GSM - Grams per Square Meter), fiber composition (e.g., 95% Cotton, 5% Spandex), and yarn count. For performance wear, verify moisture-wicking ratings and colorfastness to washing (Grade 4 or higher). Regarding construction, specify stitch density (SPI - Stitches Per Inch) and the type of seams required (e.g., flatlock for activewear or french seams for luxury items) to ensure durability and aesthetic appeal.