Add-a-leafs can be the ticket when only 1-2" of lift is desired. You may want to consider front leafs to level the vehicle or the cure the sag caused by a winch or snow plow. Rear add-a-leafs are also frequently used to beef-up the rear springs. Remember that spring fatigue is common among older vehicles and ones that have been used frequently for heavy hauling or towing.
All kits include 2 single leafs and new tie-bolts.
Superlift Add-a-leafs are designed to be used with stock leaf springs, not aftermarket springs with additional leafs or higher arch.