When sourcing from a booster cards factory, the core material is the most critical factor; high-quality cards typically use 300gsm to 350gsm black core paper to ensure opacity and professional 'snap' memory. You must also specify the surface finish, such as UV coating, matte lamination, or linen texture, to enhance durability and hand-feel. For high-value sets, ensure the factory can handle holographic foiling, cold stamping, and precise die-cutting with a tolerance of less than 0.5mm to avoid 'off-center' printing issues.