The TeraFlex heavy duty master cylinder is a solid upgrade for your Jeep Wrangler JK on larger-than-stock tires. This product has an oversized bore that allows 14% more flow. This is a recommended upgrade to provide a firmer pedal when using the Teraflex Big Brake kit. This is a great solution to a softer pedal, and may be desirable once you've installed the Big Brake Kit. This upgrade is required for 2007, 2008, and 2011 JKs. All other years would benefit from this upgrade and it is highly recommended.