When sourcing knitted fabric, the most critical technical metric is GSM (Grams per Square Meter), which determines the fabric's weight and thickness. For high-quality apparel, ensure the colorfastness rating is at least Grade 4 to prevent fading. You must also verify the shrinkage rate, which should ideally be under 5% for cotton knits and under 3% for synthetic blends. Additionally, check the pilling resistance level (ISO 12945-2) to ensure the fabric maintains a smooth surface after repeated wear.