Pucks are a cheap way to add some suspension lift to a TJ. They are spacers that go on top of the coil springs. Usually around 2-2.25". Budget Boost (or BB) is another name for them. Since you have to remove the springs to install them, they are just as much work to install as a spring lift. Actually more, because you have to remove the bumpstop cups to get them on. Spring lifts are better as you get more spring travel. But a lot of folks that do not do any hardcore off roading are happy with budget boosts/pucks to be able to fit larger tires.