I bought the S-C 4500# unit. It's waiting at home when we finish this 4 week trip. May be awhile before I use it. After getting rid of rust on the hitch where the Smart Jack makes contact, the Smart Jack has been working perfectly. Of course. The S-C 4500# got down to $212. I couldn't pass on it as a back-up. Just doing my bit to keep the economy going.