Carli Suspension 2005-16 Add-A-Packs Our progressive add a pack rear springs are a proprietary design built for us by Deaver Spring MFG. The lower overload leaf is removed and is replaced by several thinner gauge leaf springs. The O.E.M. load capacity is still maintained while traction and predictability of the rear end increase drastically. – Level 2.5″ Suspensions:Super Duties equipped with a 3-5/8″ tall block from the factory will require the factory 2″ tall Block to obtain leveled stance with the add-a-pack.Part Number: 7C3Z-5598-L and 7C3Z-5598-K – 4.5″ Suspensions:Super Duties equipped with a 2″ tall block from the factory will require the factory 3-5/8″ tall Block to attain leveled stance with the add-a-pack.Part Number: 7C3Z-5598-HB and 7C3Z-5598-JB – Supplied with U-bolts and hardware Carli Suspension 2017+ Add-A-Packs Our 6 leaf progressive add a pack rear springs are a proprietary design built for us by Deaver Spring MFG. The lower overload leaf is removed and is replaced with 6 thinner gauge leaves. The O.E.M. load capacity is maintained while improved ride is achieved. These packs are designed to eliminate the incredibly harsh rebound of the factory overload spring they replace helping to tame the medium to large bumps when paired with a Carli Suspension System. Ford 2005-2007 Progressive Add-A-Pack SKU: CS-FPAP-05 Built in the U.S.A. By Deaver Leaf Spring Smooth progressive design Supplied with U-bolts and hardware Provides 2.0" of lift O.E.M. load capacity maintained, improved ride Fitment: 2005-2007 F250/350 4x4, 3.5" Axle Tube Ford 2008-2010 Progressive Add-A-Packs SKU: CS-FPAP-08 Built in the U.S.A. By Deaver Leaf Spring Smooth progressive design Supplied with U-bolts and hardware Provides 2.0" of lift O.E.M. load capacity maintained, improved ride Fitment: 2008-2010 F250/350 4x4, 3.5" Axle Tube Ford 2011-2016 Progressive Add-A-Packs SKU: CS-FPAP-11 Built in the U.S.A. By Deaver Leaf Spring Smooth progressive design Supplied with U-bolts and hardware Provides 2.0" of lift O.E.M. load capacity maintained, improved ride Fitment: 2011-2016 F250/350 4x4, 3.5" Axle Tube Ford 2017 Progressive Add-A-Packs - Leveling SKU: CS-FPAP-LVL-17 Built in the U.S.A. By Deaver Leaf Spring Smooth Progressive Design Supplied with Bump Stop Drops, U-bolts and hardware Eliminates the Factory block and provides 1/2" of lift over stock Load capacity is maintained, ride quality is improved Fitment: 2017+ F250/350 4x4 Ford 2017 Progressive Add-A-Packs - 4.5" Lifts SKU: CS-FPAP-45-17 Built in the U.S.A. By Deaver Leaf Spring Smooth Progressive Design Supplied with 2" Block, Bump Stop Drops, U-bolts and hardware Provides 2.5" of lift over stock Load capacity is maintained, Ride quality is improved Fitment: 2017+ F250/350 4x4