Look for suppliers utilizing advanced knitting machinery, such as Italian Lonati machines, which provide superior precision and stitch consistency. Evaluate their MOQ (Minimum Order Quantity) flexibility; while standard orders may require 1,000 to 3,000 pairs per color/size, many top-tier suppliers on Made-in-China.com offer lower MOQs for stocked yarn colors. Additionally, verify if the factory provides OEM/ODM services, including custom packaging and private labeling, which are essential for brand building.