A turbine comprising: (i) a turbine wheel having an axis, (ii) a turbine housing for defining a chamber for receiving the turbine wheel for rotation of the turbine wheel about the axis, the turbine housing further defining a gas inlet, and an annular inlet passage from the gas inlet to the chamber, (iii) a ring-shaped shroud defining a plurality of slots (230; 330) and encircling the axis, each slot having a slot surface; and (iv) a nozzle ring supporting a plurality of vanes (207; 307) which extend from the nozzle ring parallel to the axis, and project through respective ones of the slots; each of the vanes having: an axially-extending vane surface which includes (i) a vane outer surface facing a radially-outer surface of the corresponding slot, (ii) an opposed vane inner surface facing a radially-inner surface of the corresponding slot, and a median line between the vane inner surface and the vane outer surface extending from a leading end of the vane to a trailing end of the vane; characterized in that: the vane is positionable with a leading surface portion (260; 368) of the vane inner surface (241; 341) contacting a corresponding leading surface portion (2461; 3462) of the respective slot surface; the vane inner surface further including a trailing surface portion (266; 366) extending along at least 33% of the median line and, which, at room temperature and when the leading surface portions are in contact, is spaced from an opposed trailing surface portion (2462; 3461) of the slot surface by a distance in the range 10 microns to 250 microns. (i) a turbine wheel having an axis, (ii) a turbine housing for defining a chamber for receiving the turbine wheel for rotation of the turbine wheel about the axis, the turbine housing further defining a gas inlet, and an annular inlet passage from the gas inlet to the chamber, (iii) a ring-shaped shroud defining a plurality of slots (230; 330) and encircling the axis, each slot having a slot surface; and (iv) a nozzle ring supporting a plurality of vanes (207; 307) which extend from the nozzle ring parallel to the axis, and project through respective ones of the slots; an axially-extending vane surface which includes (i) a vane outer surface facing a radially-outer surface of the corresponding slot, (ii) an opposed vane inner surface facing a radially-inner surface of the corresponding slot, and a median line between the vane inner surface and the vane outer surface extending from a leading end of the vane to a trailing end of the vane; characterized in that: the vane is positionable with a leading surface portion (260; 368) of the vane inner surface (241; 341) contacting a corresponding leading surface portion (2461; 3462) of the respective slot surface; the vane inner surface further including a trailing surface portion (266; 366) extending along at least 33% of the median line and, which, at room temperature and when the leading surface portions are in contact, is spaced from an opposed trailing surface portion (2462; 3461) of the slot surface by a distance in the range 10 microns to 250 microns. the vane is positionable with a leading surface portion (260; 368) of the vane inner surface (241; 341) contacting a corresponding leading surface portion (2461; 3462) of the respective slot surface; the vane inner surface further including a trailing surface portion (266; 366) extending along at least 33% of the median line and, which, at room temperature and when the leading surface portions are in contact, is spaced from an opposed trailing surface portion (2462; 3461) of the slot surface by a distance in the range 10 microns to 250 microns.