AJ Hartman Rear Adjustable Spring Perch Kit for Ford Mustang S550 (2015-2023) now available! This Rear Adjustable Spring Perch Kit allows the use of many more spring rate options in the rear. This kit will allow you to fine tune the ride height of your S550 Mustang and adjust your corner balance to help with handling. Fortune Auto Springs are not compatible with this kit. 6” Swift Springs with 65mm ID and 6” HyperCo springs with 2.5” ID are compatible. shop-fortune-auto.com #mustang #s550 #ford #fordmustang #s550mustang