A strain wave gear system, including a circular spline arranged around a longitudinal axis, a flexible spline within and coaxial with the circular spline and a wave generator within and coaxial with the flexible spline. The wave generator is non-circular in a plane perpendicular to the longitudinal axis. The flexible spline is arranged to flex in response to rotation of the wave generator. The wave generator is configured to rotate about the longitudinal axis such that the flexible spline is arranged to selectively engage with the circular spline. The strain wave gear system further includes a bearing arrangement between and coaxial with the wave generator and the flexible spline. The bearing arrangement comprises a plurality of bearings and a cage arranged to retain the plurality of bearings. The plurality of bearings are located at more than two axial positions within the cage.