SPF4396-24K is the upgrade replacement for the OEM sway bar size on the 2015-2021 Subaru WRX and WRX STI - if you want to retain the front sway bar but remove the flex and deflection from the OEM bushings for uncompromised function and impact from the front bar; this is an ideal bang-for-the-buck repair and upgrade item. Sway bar mount bushings are one of the most underappreciated components in your suspension system. Responsible for anchoring the sway bars and facilitating proper function and body control of your vehicle the OEM rubber bushings are tasked with quite a job and in-turn wear quickly compromising the effectiveness of your sway bar and contributing to a loose, sloppy feeling on the road over time. SuperPro's sway bar mount bushings are designed to fit the OEM designed hardware and mountings - no generic one-size-fits all bushings and cheap universal hardware here - each bushing is designed to integrate into the factory suspension design and function. Additionally grease retention technology is used in each bushing we make for a lifetime of smooth and silent operation turning a frequent maintenance item into a one-time repair upgrade to keep your vehicle driving like new; for life.