Features:
1) Materials: 7001-T6/T9, 7075-T9 alloy
2) High strength: 660Mpa
3) Light weight: 7001 or 7075 aluminum alloy is lighter than 6063
    and 6061
4) Tightness tolerance:
    a) Inner diameter: ±0.02mm
    b) Outer diameter: ±0.02mm
5) Weight: ± 0.5%
6) Straightened to 0.15mm