When sourcing asphalt shingles, the most critical factor is the base material, which should be high-quality fiberglass mat to ensure tensile strength and tear resistance. You must verify the bitumen (asphalt) content and quality, as it determines the shingle's waterproofing capability and flexibility. Additionally, check the granule adhesion; high-quality ceramic-coated mineral granules protect the asphalt from UV degradation and provide color stability. For international standards, ensure the products meet ASTM D3462 or EN 544 benchmarks.