The most critical factor is the base material, typically cellulose kraft paper or plastic (PVC/PP). For maximum cooling efficiency, prioritize high-density cellulose paper treated with anti-rot and wetting agents. Ensure the paper has a cross-fluted configuration (e.g., 5090 or 7090 models) to maximize the surface area for evaporation. If the environment is highly humid or prone to algae, plastic cooling pads are more durable and easier to clean, though they offer slightly lower evaporation efficiency.