When evaluating microfiber, the most critical metric is GSM (Grams per Square Meter), which determines thickness and absorbency; for general cleaning, 250-300 GSM is standard, while premium detailing towels require 400+ GSM. Additionally, verify the blend ratio, typically 80% polyester and 20% polyamide; a higher polyamide content increases water absorption and softness. You should also check the denier count, as true microfiber must be less than 1 denier per filament to ensure effective trapping of dust and bacteria.