Selecting the correct Lenticular Lens (LPI - Lines Per Inch) is critical for the desired visual effect. For handheld cards like business cards or trading cards, a high LPI (75 to 100 LPI) is recommended for sharp, high-definition 3D and flip effects at close range. For posters or larger displays, a lower LPI (20 to 40 LPI) is better suited for long-distance viewing. Ensure the material is PET (Polyethylene Terephthalate) rather than PVC, as PET offers superior transparency, better environmental compliance (BPA-free), and higher durability.