An indexable cutting insert (20, 120) comprising: opposing upper and lower end surfaces (22, 24) with a continuous peripheral side surface and a central axis extending therebetween, upper and lower peripheral edges (28, 30) formed at the intersection of the peripheral side surface and the upper and lower end surfaces (22, 24), respectively, and a number N upper cutting edges formed on the upper peripheral edge where N ≥ 2, the peripheral side surface including: a continuous upper relief surface adjacent the upper peripheral edge which continuous upper relief surface is non-circular in a cross-section taken in a first horizontal plane (P H 1) perpendicular to the central axis, wherein: each upper cutting edge exhibits mirror symmetry about a respective bisector plane (P B) containing the central axis; in an end view of the cutting insert (20, 120), the upper peripheral edge is non-circular and exhibits N-fold rotational symmetry about the central axis; and in a side view of the cutting insert (20, 120), each upper cutting edge is non-linear, and wherein: the lower peripheral edge is identical to the upper peripheral edge, having a plurality of N lower cutting edges formed thereon, characterised in that the peripheral side surface further includes a continuous upper abutment surface spaced apart from the upper peripheral edge which upper abutment surface is circular in a cross-section taken in a second horizontal plane perpendicular to the central axis (Al). opposing upper and lower end surfaces (22, 24) with a continuous peripheral side surface and a central axis extending therebetween, upper and lower peripheral edges (28, 30) formed at the intersection of the peripheral side surface and the upper and lower end surfaces (22, 24), respectively, and a number N upper cutting edges formed on the upper peripheral edge where N ≥ 2, the peripheral side surface including: a continuous upper relief surface adjacent the upper peripheral edge which continuous upper relief surface is non-circular in a cross-section taken in a first horizontal plane (P H 1) perpendicular to the central axis, wherein: each upper cutting edge exhibits mirror symmetry about a respective bisector plane (P B) containing the central axis; in an end view of the cutting insert (20, 120), the upper peripheral edge is non-circular and exhibits N-fold rotational symmetry about the central axis; and in a side view of the cutting insert (20, 120), each upper cutting edge is non-linear, and wherein: the lower peripheral edge is identical to the upper peripheral edge, having a plurality of N lower cutting edges formed thereon, characterised in that the peripheral side surface further includes a continuous upper abutment surface spaced apart from the upper peripheral edge which upper abutment surface is circular in a cross-section taken in a second horizontal plane perpendicular to the central axis (Al). each upper cutting edge exhibits mirror symmetry about a respective bisector plane (P B) containing the central axis; in an end view of the cutting insert (20, 120), the upper peripheral edge is non-circular and exhibits N-fold rotational symmetry about the central axis; and in a side view of the cutting insert (20, 120), each upper cutting edge is non-linear, and wherein: the lower peripheral edge is identical to the upper peripheral edge, having a plurality of N lower cutting edges formed thereon, characterised in that the peripheral side surface further includes a continuous upper abutment surface spaced apart from the upper peripheral edge which upper abutment surface is circular in a cross-section taken in a second horizontal plane perpendicular to the central axis (Al). the lower peripheral edge is identical to the upper peripheral edge, having a plurality of N lower cutting edges formed thereon, characterised in that the peripheral side surface further includes a continuous upper abutment surface spaced apart from the upper peripheral edge which upper abutment surface is circular in a cross-section taken in a second horizontal plane perpendicular to the central axis (Al).