When evaluating circular knitted fabrics, you must prioritize GSM (Grams per Square Meter) to ensure the weight meets your specific garment requirements. Key technical factors include yarn count (e.g., 30s, 40s), which determines fineness, and stitch density, which affects opacity and hand-feel. For performance wear, verify the spandex/elastane percentage for stretch recovery. Additionally, ensure the fabric has undergone anti-pilling and shrinkage control treatments, aiming for a shrinkage rate of less than 5%.