When purchasing natural rubber latex (NRL), the most critical factor is the Dry Rubber Content (DRC), which typically ranges from 60% for concentrated latex to lower percentages for field latex. You must also verify the Ammonia content (High Ammonia HA or Low Ammonia LA), as it acts as a preservative to prevent premature coagulation. Other vital parameters include Volatile Fatty Acid (VFA) number, KOH number (indicating stability), and mechanical stability time (MST), which should ideally be above 650 seconds for industrial processing.