worm screw lift; Safely self locking, Positioning Precision, Heavy Duty, Uniform Lifting Speed, Low Efficiency, Use Infrequentl worm screw liftConfiguration: Worm Gear, Worm Shaft, Taper Roll Bearings, Seals, Housing, Self-locking Trapezoidal Screw,etc.* Model: RN-0.5ton, RN-1 ton, RN-2 ton, RN-3 ton, RN-5 ton, RN-10 ton, RN-15 ton, RN-20 ton, RN-30 ton, RN-40 ton, RN-50 ton, RN-100 ton.* Safely ...