The ReadyLIFT Pro Plus 4 lift kit is specifically designed for 2015-2021 Toyota Tundra TRD Pro trucks, offering a 4" front lift while retaining the original 2" factory lift, equating to a total height similar to a 6" lift on standard Tundras. This kit allows continued use of factory Bilstein/Fox coil-overs and reservoir rear shocks, and maintains all factory TRD Pro suspension components. It is compatible exclusively with 2015-2021 Tundra TRD Pro models equipped with Bilstein/Fox coilover shocks, but incompatible with the TRD rear sway bar option and the factory front skid plate. The kit requires factory 20" wheels and is not suitable for some factory 18" wheels, though properly sized aftermarket wheels are acceptable. The 44-5640 Pro Plus 4 inch lift kit features laser cut, CNC bent, welded, and boxed subframe drop assemblies that enhance suspension geometry and increase ground clearance by 2 inches. Its iron knuckles are CNC machined for a precise fit and allow retention of factory tie rods, eliminating the need for cutting or replacement. The 4 inches of lift is achieved through offset top mount spacer design attached to the factory coilover/strut, ensuring a factory ride quality and maintaining the original track width. The kit includes a differential drop kit for easy installation and correct positioning of the differential, preserving optimal CV axle and drive line angles. It focuses on maintaining proper alignment and geometry specifications, thereby reducing tire wear. The rear of the kit contains OEM-style cast iron rear lift blocks, longer u-bolts with hardware, bump stop extensions, sway bar frame mount brackets, and shock stem extensions for the Bilstein/Fox reservoir shocks. The kit supports up to 35" tires on a 9" wheel with a +25 offset, minimizing the risk of rubbing. Removal of front mud flaps may be necessary depending on tire tread design.