1. Material D2, high strength and wear resistance; 2. Deep cold treatment in ultra-empty space, with hardness HRC60~ 62 and balanced hardness; 3. High coaxiality (single coaxiality < 0.002mm, combined coaxiality ≤ 0.005mm); 4. High positioning accuracy, no adjustment, and interchangeable use; 5. Products can replace similar products of European level.