Abstract: A cutting insert for mounting on a milling cutter has a generally quadrangular shape with top and bottom surfaces, a pair of opposite first side surfaces intersecting the top surface at first cutting edges and a pair of opposite second side surfaces intersecting the top surface at second edges. Each second edge has a front cutting portion oriented substantially transversely to an adjacent first cutting edge and meeting therewith via a cutting corner. Each of the first and second side surfaces has upper and lower sections adjacent respective top and bottom surfaces, which sections have leading portions adjacent their associated cutting corner and trailing portions remote therefrom. The trailing portion of the lower section of each second side surface is at least slightly inwardly depressed relative to the leading portion of the lower section and is substantially inwardly depressed relative to the associated trailing portion of the upper section of the second side surface.