When sourcing fine cotton, the Thread Count (TC) and Yarn Count (s) are the most critical indicators of quality. For premium applications, look for a yarn count of 60s, 80s, or 100s; higher numbers indicate finer, smoother threads. Additionally, verify the GSM (Grams per Square Meter) to ensure the fabric weight aligns with your needs (e.g., 90-120 GSM for shirting). Always request data on colorfastness to washing (Grade 4 or higher) and shrinkage rates, which should ideally be under 3% for pre-shrunk high-end textiles.