A cutting insert, for internal grooving comprising: a front surface; a rear surface; a peripheral surface extending between the front and rear surfaces (34, 36); a cutting portion; a mounting portion comprising: a lower rear surface; and exactly two insert protuberances, a first insert protuberance and a second insert protuberance, protruding from the lower rear surface in a direction away from the front surface, each insert protuberance (52, 54) comprising: two insert protuberance side surfaces extending in a direction away from the lower rear surface; and an insert protuberance upper surface located between the two insert protuberance side surfaces and distal the lower rear surface; and a through bore, passing through the front and rear surfaces (34, 36); characterised in that the two insert protuberance side surfaces on the first insert protuberance form first and second insert protuberance side surfaces (64, 66) that converge towards each other in a direction from the peripheral surface towards the through bore, to form a protuberance wedge angle (2α) having a bisector; the two insert protuberance side surfaces on the second insert protuberance form third and fourth insert protuberance side surfaces (68, 70) that converge towards each other in a direction from the peripheral surface towards the through bore; in a rear view of the cutting insert a minimum first distance between an imaginary line laying on the first insert protuberance side surface and the fourth insert protuberance side surface is greater than a second distance between the second insert protuberance side surface and an imaginary line laying on the third insert protuberance side surface; and in a rear view of the cutting insert the angle between the third insert protuberance side surface and the bisector is equal to half the protuberance wedge angle (2α). a front surface; a rear surface; a peripheral surface extending between the front and rear surfaces (34, 36); a cutting portion; a mounting portion comprising: a lower rear surface; and exactly two insert protuberances, a first insert protuberance and a second insert protuberance, protruding from the lower rear surface in a direction away from the front surface, each insert protuberance (52, 54) comprising: two insert protuberance side surfaces extending in a direction away from the lower rear surface; and an insert protuberance upper surface located between the two insert protuberance side surfaces and distal the lower rear surface; and a lower rear surface; and exactly two insert protuberances, a first insert protuberance and a second insert protuberance, protruding from the lower rear surface in a direction away from the front surface, each insert protuberance (52, 54) comprising: two insert protuberance side surfaces extending in a direction away from the lower rear surface; and an insert protuberance upper surface located between the two insert two insert protuberance side surfaces extending in a direction away from the lower rear surface; and an insert protuberance upper surface located between the two insert protuberance side surfaces and distal the lower rear surface; and a through bore, passing through the front and rear surfaces (34, 36); characterised in that the two insert protuberance side surfaces on the first insert protuberance form first and second insert protuberance side surfaces (64, 66) that converge towards each other in a direction from the peripheral surface towards the through bore, to form a protuberance wedge angle (2α) having a bisector; the two insert protuberance side surfaces on the second insert protuberance form third and fourth insert protuberance side surfaces (68, 70) that converge towards each other in a direction from the peripheral surface towards the through bore; in a rear view of the cutting insert a minimum first distance between an imaginary line laying on the first insert protuberance side surface and the fourth insert protuberance side surface is greater than a second distance between the second insert protuberance side surface and an imaginary line laying on the third insert protuberance side surface; and in a rear view of the cutting insert the angle between the third insert protuberance side surface and the bisector is equal to half the protuberance wedge angle (2α).