When evaluating concrete products, the most critical factor is Compressive Strength, typically measured in MPa or PSI (e.g., C30/37 for structural use). You must verify the Water-Cement Ratio, as a lower ratio generally indicates higher durability and lower permeability. For reinforced concrete, ensure the Rebar Grade and Placement meet structural engineering standards to prevent corrosion and structural failure. Additionally, check the Dimensional Tolerance; high-quality suppliers should maintain a variance of less than ±3mm to ±5mm depending on the product size.