An indexable, single-sided cutting insert comprising: opposing upper and lower surfaces with a peripheral side surface extending therebetween and a central axis (Ac) passing therethrough, the upper and lower surfaces having shapes that differ from one another; first and second clamping bores extending between and opening out at the upper and lower surfaces , the first and second clamping bores having first and second bore axes (AB1, AB2), respectively; and first and second primary cutting edges formed at the intersection of the upper surface and the peripheral side surface ; wherein the lower surface includes: a planar base surface , first and second annular recesses communicating with the first and second clamping bores , respectively, and first and second recess channels extending from the first and second clamping bores , respectively, to the peripheral side surface , the first and second recess channels extending parallel to a longitudinal first plane (P1) containing the central axis (Ac), wherein the first and second annular recesses intersect first and second bore neck-portions of the first and second clamping bores at first and second minimum bore diameters (DBMIN1, DBMIN2), respectively, and characterized in that : the first and second annular recesses include first and second annular shoulder surfaces , respectively, the first and second annular shoulder surfaces intersect the first and second bore neck-portions , respectively, and the first and second annular shoulder surfaces are coplanar and perpendicular to the central axis (Ac). opposing upper and lower surfaces with a peripheral side surface extending therebetween and a central axis (Ac) passing therethrough, the upper and lower surfaces having shapes that differ from one another; first and second clamping bores extending between and opening out at the upper and lower surfaces , the first and second clamping bores having first and second bore axes (AB1, AB2), respectively; and first and second primary cutting edges formed at the intersection of the upper surface and the peripheral side surface ; wherein the lower surface includes: a planar base surface , first and second annular recesses communicating with the first and second clamping bores , respectively, and first and second recess channels extending from the first and second clamping bores , respectively, to the peripheral side surface , the first and second recess channels extending parallel to a longitudinal first plane (P1) containing the central axis (Ac), a planar base surface , first and second annular recesses communicating with the first and second clamping bores , respectively, and first and second recess channels extending from the first and second clamping bores , respectively, to the peripheral side surface , the first and second recess channels extending parallel to a longitudinal first plane (P1) containing the central axis (Ac), wherein the first and second annular recesses intersect first and second bore neck-portions of the first and second clamping bores at first and second minimum bore diameters (DBMIN1, DBMIN2), respectively, and characterized in that : the first and second annular recesses include first and second annular shoulder surfaces , respectively, the first and second annular shoulder surfaces intersect the first and second bore neck-portions , respectively, and the first and second annular shoulder surfaces are coplanar and perpendicular to the central axis (Ac). the first and second annular recesses include first and second annular shoulder surfaces , respectively, the first and second annular shoulder surfaces intersect the first and second bore neck-portions , respectively, and the first and second annular shoulder surfaces are coplanar and perpendicular to the central axis (Ac). <EOS>