The quality of a cashmere suit is primarily determined by the fiber fineness and length. Look for suppliers offering Grade A cashmere, which typically has a diameter of under 15.5 microns and a fiber length of 34-36mm. This ensures the suit is incredibly soft, lightweight, and resistant to pilling. Additionally, verify if the fabric is 100% pure cashmere or a cashmere-wool blend (e.g., 70/30 or 90/10); while blends increase durability for daily office wear, pure cashmere offers the highest prestige and thermal regulation.