Buyers must prioritize Tensile Strength and Elongation at Break; a high elongation rate (often >300%) ensures the film can stretch into deep cavities without tearing. Additionally, verify the Thickness Uniformity, as variations can lead to surface defects on the finished part. For vacuum bagging processes, ensure the film is Perforated (P3, P31, or custom patterns) to allow controlled resin and air flow, and check for Silicone-free certification to prevent contamination of parts intended for secondary bonding or painting.