When sourcing used LED displays, you must prioritize the Pixel Pitch (P-value), as it determines the viewing distance and resolution. For indoor use, P1.2 to P3.9 is standard, while outdoor displays typically range from P4 to P10. Additionally, verify the Refresh Rate (ideally ≥1920Hz or 3840Hz) to avoid flickering on camera, and check the Brightness levels (measured in Nits); outdoor screens require at least 5000-7000 Nits to remain visible in direct sunlight, whereas indoor screens need 800-1200 Nits.