I'm getting the 4 pc combo kit for Christmas from my wife. FWIW I'm currently using the 18v Firestorm tools. Contrary to the opinions I've seen here they performed admirably for the cost point they're at. I would have no complaints about them but am looking to upgrade to a sturdier pro model. I noticed that the part # for the hammer drill in the kit is different from the individually purchased one. R841150 is included in the combo pack and the individual one is R841151. Is thier a difference between these two products or is the # difference only an inventory control measure? Thanks John Merry Christmas!