When evaluating a sun lighter, the most critical component is the parabolic mirror quality. Ensure the reflective surface is made of high-grade polished aluminum or stainless steel to prevent oxidation and maintain a reflectivity rate above 90%. The focal point must be precisely engineered; a well-defined focal zone ensures ignition within 2-5 seconds under direct sunlight. Additionally, check the arm/bracket durability to ensure it can securely hold various tinder types like dry leaves, paper, or incense.