When evaluating UV protection film, you must prioritize the UV Rejection Rate, which should ideally be 99% or higher to prevent interior fading and skin damage. Additionally, consider the Visible Light Transmission (VLT); a lower VLT (e.g., 5-20%) provides more privacy, while a higher VLT (e.g., 50-70%) maintains natural light. The Total Solar Energy Rejection (TSER) is a critical metric for heat insulation—look for values above 40-50% for energy efficiency. Lastly, ensure the film thickness is at least 2 mil for durability and ease of installation.