When sourcing microwave absorbers, the most critical factor is the frequency range (GHz) they are designed to attenuate. You must specify whether you need narrowband (tuned) or broadband performance. Key metrics include Reflection Loss (measured in dB), where a higher negative value (e.g., -20dB) indicates 99% absorption efficiency. Additionally, consider the material base, such as silicone, urethane foam, or epoxy, depending on whether the application requires flexibility, weather resistance, or structural rigidity.