... , Hardened Couplers are Adopted, Heavy Duty Steel Props Steel props (light duty) I: 1,920-3,500mm, 26 ... ,900mm, 29.98lbs2,920-4,500mm, 33.51lbsSteel props (heavy duty) I: 1,700-2,900mm, 54.01lbs2,200- ... ,900mm, 66.14lbs2,700-4,900mm, 77.16lbsSteel props (heavy duty) II: 3,251-4,877mm, 59.08lbs2,642- ... 505mm, 46.30lbs1,803-2,997mm, 40.34lbsHigh quality steel usedHardened couplers are adoptedLoad test passed ...