... Shell- use advance aluminum alloy, light quantity, and treat with anodized finish inside and outside, polyester powder coated on surface ... arbitrary).8,Self-lock-self-lock function, avoid reversing, with steady and reliable acting part. 9,Mounting- bottom mounting ... linkage.11,Wormgear- adopt cam design, large connecting surface with worm rod, big output torque, balance and anti-abrasion, long service ...