three-row roller slewing ring has 3 seat-rings, Upper Orbit, Nether Orbit and Radial Orbit are separated individually, it makes the load of each row of the rollers can be confirmed, so it can undertake all kinds of different load simultaneously and it's Carrying Capacity is the biggest among four models,one more thing,the axial&radial size are rather large to some extent and the structure is very firm,so it is especially suitable for many heavy-duty machines which require bigger diameter,such as,Bucket-Wheel Excavator,wheeled Crane,Shipyard Crane,heavy-duty Truck Crane,and so on.