Buyers must evaluate the base material (PET, PVC, or PE), as this determines clarity and heat resistance. The adhesive type (acrylic vs. silicone) is critical; acrylic offers high initial tack, while silicone is preferred for high-temperature applications. Ensure the thickness (measured in microns or mils) aligns with the application—thinner films (25-50μm) are for labels, while thicker films (100μm+) are for surface protection. Additionally, verify the light transmission rate (ideally >90%) and haze value (<1%) to ensure optical clarity.