Microfiber density is measured in GSM (Grams per Square Meter). More GSM is always better because denser microfiber holds more water or product and lasts longer. The higher the number, the thicker, plushier and softer the microfiber towel generally is.The higher the density, the higher the price however. A 200-250GSM microfiber towel is suited for general purpose cleaning while 300+ is considered a professional grade and is ideal for delicate surfaces like car paint.