A brake kit contains the brake disc, brake pads, the brake caliper, brake lines and mounting hardware. Performance or Big brake kits are engineered to improve your stopping distance by a bigger rotor size and piston bore. By increasing the surface area of your brake rotor, a larger amount of clamping force is possible by the 4, 6, or 8 piston calipers. Performance brake kits also offer better thermal management to prevent damaging effects that other standard factory installed systems suffer from.