An ion guide comprising: a plurality of electrodes arranged to form a multipole ion guide, wherein the plurality of electrodes comprises plural groups of electrodes, and each group of electrodes comprises plural electrodes that are axially spaced apart from one another; and one or more rigid support members , wherein the electrodes of plural groups of electrodes are attached to one of the rigid support members ; wherein one or more of the electrodes comprises a curved metal sheet, plate or strip; wherein the plural groups of electrodes are angularly spaced apart from one another; characterised in that : the electrodes of two of the angularly spaced groups of electrodes are attached to a single rigid support member ; each curved metal sheet, plate or strip electrode comprises one or more protrusions; each rigid support member comprises plural holes; each electrode protrusion is arranged inside a hole of a rigid support member; each curved metal sheet, plate or strip electrode comprises one or more recesses adjacent to one or more of the one or more protrusions such that when each protrusion is fully inserted into the corresponding hole in the rigid support member, the curved metal sheet, plate or strip electrode will lie flat with respect to the surface of the rigid support member; and each curved metal sheet, plate or strip electrode is soldered to one of the one or more rigid support members. a plurality of electrodes arranged to form a multipole ion guide, wherein the plurality of electrodes comprises plural groups of electrodes, and each group of electrodes comprises plural electrodes that are axially spaced apart from one another; and one or more rigid support members , wherein the electrodes of plural groups of electrodes are attached to one of the rigid support members ; wherein one or more of the electrodes comprises a curved metal sheet, plate or strip; wherein the plural groups of electrodes are angularly spaced apart from one another; characterised in that : the electrodes of two of the angularly spaced groups of electrodes are attached to a single rigid support member ; each curved metal sheet, plate or strip electrode comprises one or more protrusions; each rigid support member comprises plural holes; each electrode protrusion is arranged inside a hole of a rigid support member; each curved metal sheet, plate or strip electrode comprises one or more recesses adjacent to one or more of the one or more protrusions such that when each protrusion is fully inserted into the corresponding hole in the rigid support member, the curved metal sheet, plate or strip electrode will lie flat with respect to the surface of the rigid support member; and each curved metal sheet, plate or strip electrode is soldered to one of the one or more rigid support members. the electrodes of two of the angularly spaced groups of electrodes are attached to a single rigid support member ; each curved metal sheet, plate or strip electrode comprises one or more protrusions; each rigid support member comprises plural holes; each electrode protrusion is arranged inside a hole of a rigid support member; each curved metal sheet, plate or strip electrode comprises one or more recesses adjacent to one or more of the one or more protrusions such that when each protrusion is fully inserted into the corresponding hole in the rigid support member, the curved metal sheet, plate or strip electrode will lie flat with respect to the surface of the rigid support member; and each curved metal sheet, plate or strip electrode is soldered to one of the one or more rigid support members. <EOS>