When evaluating a one-piece flush valve toilet, prioritize high-temperature calcined ceramic (fired at over 1280°C) to ensure a water absorption rate of less than 0.5%, which prevents cracking and odors. The glaze quality is critical; look for self-cleaning nano-glaze applied to the entire trapway to ensure smooth waste passage. Additionally, verify the flush valve diameter (typically 2.5 to 3 inches) and the Map (Maximum Performance) score, aiming for at least 800g to 1000g for commercial-grade efficiency.