This Axle-Back system uses high-flow straight-through mufflers designed to deliver a deep, sporty tone from your 2015-2020 Subaru WRX and 2015-2018 WRX STI with a 2.0 or 2.5L engine. This system is constructed from 304 stainless steel providing maximum durability. It uses 2.5-inch tubing and a polished 4-inch tip. Simple installation is made possible by using the factory mounting points.