A lock for a ground engaging tool may have a first diameter body portion, a neck portion extending from the body portion along a rotational axis of the lock and having a second diameter smaller than the first diameter, and a head portion extending from the neck portion along the rotational axis. The head portion may have first and second generally planar end surfaces extending from a bottom surface to a top surface, and first and second cam surfaces, which connect the end surfaces and each include a convex portion and a concave portion.