A slewing bearing ring is a rotational rolling-element bearing that typically supports a heavy but slow-turning or slow-oscillating load, often a horizontal platform such as a conventional crane, or the wind-facing platform of a horizontal-axis windmill. (To 'slew' means to turn without change of place.).115 Inch Four-Point Contact 2922 x 3376 x 174mm Ball Slewing Ring Bearing with No Gear