When evaluating PU foam blocks, the most critical factor is density (measured in kg/m³ or lb/ft³), as it directly correlates with durability and support. For high-end furniture or industrial applications, a density of ≥30kg/m³ is recommended. Additionally, you must verify the Indentation Load Deflection (ILD) or Hardness, which determines the foam's firmness. For specialized applications, inquire about the cell structure (open-cell vs. closed-cell) to ensure the material meets your needs for breathability or insulation.