When sourcing these high-tech promotional tools, you must prioritize LED Screen Resolution and Brightness. Look for a pixel pitch of P2.5 to P3.75 for clear imagery at close range, and a brightness level of at least 800-1000 nits to ensure visibility in direct sunlight. Additionally, verify the Battery Capacity (typically 10,000mAh to 20,000mAh), which should support 6-10 hours of continuous playback. The backpack material itself should be water-resistant (IP65 rated for the screen) and feature ergonomic breathable mesh to ensure wearer comfort during long promotional events.