The TeraFlex JK brake master cylinder compensates for the larger caliper piston size found in the TeraFlex JK front Big Brake Kit with an oversized bore that has 14% more flow for greater fluid volume. This kit also restores a firmer pedal feel. This is a great solution to a softer pedal that may appear once you have had the Big Brake Kit. **We highly recommend this master cylinder for 2007-2011 JKs with the Big Brake Kit to provide a firm pedal feel. 2012+ JKs do not need this kit.** Note: Specific steps must be taken when bleeding the brake system, a bench bleed is recommended before installing the master cylinder into the Jeep. Slowly pump the pedal during the bleed process to avoid seal damage.