An idler or segmented idler having a central axle and a bearing surface provided concentrically with and radially outwardly from the axle, the idler including: a plurality of sleeve segments (102.1-102.5) which fit together end-to-end thereby to define a cylindrical segmented sleeve which presents the bearing surface, there being plural variants of sleeve segments, wherein each sleeve segment includes an abutting formation at each axial end thereof, configured to abut against an adjacent sleeve segment or other component, wherein adjacent abutting formations permit adjacent sleeve segments to be joined together, so that their respective portions of the bearing surface are aligned and seemingly continuous; a pair of annular ring bearings fixed on their inner surface to the axle and permitting rotation of the segmented sleeve relative to the axle; an intermediate support member which is hollow and cylindrical and arranged between the axle and the segmented sleeve, the support member being mounted by means of the bearings concentrically with, and to rotate about, the axle, thus having an axis of rotation coaxial with the axle; and at least some of the sleeve segments having an inner radially projecting support wall thereby to support the segmented sleeve intermediate its ends, characterised in that the abutting formation includes an interlock configuration configured to provide a frictional fit between two adjacent sleeve portions and interlock adjacent sleeve segments, and in that there is a centre sleeve segment (102.3) which is symmetrical in that it has the same abutting formation at each axial end. having a central axle and a bearing surface provided concentrically with and radially outwardly from the axle, the idler including: a plurality of sleeve segments (102.1-102.5) which fit together end-to-end thereby to define a cylindrical segmented sleeve which presents the bearing surface, there being plural variants of sleeve segments, wherein each sleeve segment includes an abutting formation at each axial end thereof, configured to abut against an adjacent sleeve segment or other component, wherein adjacent abutting formations permit adjacent sleeve segments to be joined together, so that their respective portions of the bearing surface are aligned and seemingly continuous; a pair of annular ring bearings fixed on their inner surface to the axle and permitting rotation of the segmented sleeve relative to the axle; an intermediate support member which is hollow and cylindrical and arranged between the axle and the segmented sleeve, the support member being mounted by means of the bearings concentrically with, and to rotate about, the axle, thus having an axis of rotation coaxial with the axle; and at least some of the sleeve segments having an inner radially projecting support wall thereby to support the segmented sleeve intermediate its ends, a plurality of sleeve segments (102.1-102.5) which fit together end-to-end thereby to define a cylindrical segmented sleeve which presents the bearing surface, there being plural variants of sleeve segments, wherein each sleeve segment includes an abutting formation at each axial end thereof, configured to abut against an adjacent sleeve segment or other component, wherein adjacent abutting formations permit adjacent sleeve segments to be joined together, so that their respective portions of the bearing surface are aligned and seemingly continuous; a pair of annular ring bearings fixed on their inner surface to the axle and permitting rotation of the segmented sleeve relative to the axle; an intermediate support member which is hollow and cylindrical and arranged between the axle and the segmented sleeve, the support member being mounted by means of the bearings concentrically with, and to rotate about, the axle, thus having an axis of rotation coaxial with the axle; and at least some of the sleeve segments having an inner radially projecting support wall thereby to support the segmented sleeve intermediate its ends, characterised in that the abutting formation includes an interlock configuration configured to provide a frictional fit between two adjacent sleeve portions and interlock adjacent sleeve segments, and in that there is a centre sleeve segment (102.3) which is symmetrical in that it has the same abutting formation at each axial end.