Crane Slewing Bearing or slew[ing] 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, a swing yarder, or the wind-facing platform of a horizontal-axis windmill.

 
Crane Slewing Bearings are machine elements which absorb all axial and radial forces and the resulting tilting moments in a single self-retaining and ready-to-install unit.

Their low profile and an excellent weight/performance ratio, open center, and the possibility of an integrated gearing make Rotek slewing bearings ideal structural components.