When selecting aluminium tubes, you must prioritize material grade (e.g., 6061, 6063, or 7075) based on your application. For structural use, 6061-T6 offers excellent strength and weldability, while 6063 is preferred for architectural purposes due to its superior surface finish. Ensure the wall thickness tolerance meets international standards like ASTM B210 or EN 755, and verify the temper designation (such as T5 or T6) to ensure the mechanical properties align with your load-bearing requirements.