When purchasing wholesale silk thread, you must prioritize denier (thickness) and ply (number of strands). For high-end garment manufacturing, Grade 6A mulberry silk is the industry gold standard, representing the highest quality in terms of strength and luster. Ensure the thread has a uniform twist to prevent knotting in high-speed industrial sewing machines. Additionally, verify the colorfastness rating (ISO 105-C06) to ensure the dye does not bleed during subsequent fabric processing or washing.