I bought a four bike hitch mounted rack that came with an 8' cable lock.  With the 8' cable lock, I was unable capture every wheel and every frame, so this lock was needed.  While I was 1000 miles from home on a family vacation, the mechanism in the hitch provided cable lock broke and I was really glad I had this one. The lesson learned is any lock is better than no lock, so having a backup is a good idea.  I gave this lock four starts because it is too small of diameter to prevent any slightly motivated thief, although the same can probably be said for the hitch provided cable that is nearly twice the diameter. In combination with a second cable it provided me with a satisfactory level of comfort to take the family in to a restaurant provided I had a view of my vehicle from my table.