A ground engaging tool system comprises a ground engaging tool such as a tip, an adapter mounted to or part of a work tool, and a rotating lock member. The ground engaging tool is attached to the adapter, and a post portion of the adapter slides into a slot provided on the lock. The lock is rotated so that the entrance to the slot is blocked and the post cannot slide out of the slot. The lock in this position is in a locking position, and the retention of the post in the slot of the lock retains the ground engaging tool to the adapter.