Strain wave gear

A strain wave gear having a wave generator which is rotatably mounted in a radially flexible sleeve having external toothing, and having a first rigid hollow wheel with internal toothing, the internal toothing of the first rigid hollow wheel meshing with the external toothing of the radially flexible sleeve, and having a second rigid hollow wheel with internal toothing, the internal toothing of the second rigid hollow wheel meshing with the external toothing of the radially flexible sleeve, wherein the wave generator by means of a single radially flexible roller bearing is mounted so as to be rotatable relative to the radially flexible sleeve, said radially flexible roller bearing having a first rolling-element row having first rolling elements, and a second rolling-element row having second rolling elements, the second rolling-element row being axially offset in relation to the first rolling-element row, wherein

• a. the roller bearing has an external ring with which the first rolling elements of the first rolling-element row and the second rolling elements of the second rolling-element row are in direct contact, and/or wherein
• b. the roller bearing has an internal ring with which the first rolling elements of the first rolling-element row and the second rolling elements of the second rolling-element row are in direct contact.