The invention relates to a turbine (2) comprising a housing (4) and at least one adjustable row of guide vanes (7), said row (7) having a plurality of guide vanes (8) distributed around the periphery. Each guide vane (8) is mounted in the housing (4) and is fixedly connected outside the housing (4) to a lever (18). In addition, the turbine (2) comprises an adjusting ring (20), which ring (20) can be adjusted in the peripheral and axial directions and on which ring (20) the levers (18) are pivotally mounted. In order to reduce the amount of maintenance required, according to the invention a number of ball rollers (25) are distributed around the periphery, each ball roller (25) having a bearing shell (27), a number of supporting ball bearings (29) movably mounted in said shell (27) and a running ball bearing (26) rollably mounted on said supporting ball bearings (29). The ball rollers (25) are fastened to the housing (4) or the adjusting ring (20) and the adjusting ring (20) is mounted on the running ball bearings (26), or the running ball bearings (26) are mounted on the housing.