Note: bumpstop spacers are one thing, coil spacers are another. This post is about bumpstops and related topics, including bumpstop spacers.
Bump stops are the bubber bumpers inside you coil springs. The bumpstops are mounted to frame or axle housing, I forgot which. I think bumpstops are mounted to axle housing for front of Jeep, and frame for rear of Jeep.
Stock Jeeps already have stock bumpstops.
When guy(s) tell you to get bumpstops or add bumpstops, what they really mean is longer bumpstops aka extended bumpstops.
Longer bumpstops are acheived by one of a few possible methods: You can install longer bumpstops (made of polyurothane), or you can install bumpstop spacers between you stock rubber bumpstops and their mounting point, or you can install a spacer in the place where stock rubber bump stop lands.
Usually spacers are made of aluminum, but the best spacers are made of rubber. I prefer rubber spacers because they add some extra cushion in addition to spacing.
Metalcloak makes good rubber bumpstop spacers for front axle. Not sure if they make them for rear.
Here is what I recommend to extend front bumpstops AND add some cushion for a softer landing when suspension bottoms on big bumps AND won't get caught in coil (won't scrape side of coil).
Buy Metalcloak rubber bumpstop spacers that mount to front axle housing where the stock rubber bump stops land (front bump stops are mounted at top of coil spring). The Metalcloak rubber bumpstop spacers come in 1", 2", 3", and so on. Get as much spacer as is appropriate.
For rear coils, buy a spacer that mounts to frame between frame and stock rubber bump stop. I think aluminum spacers are the only option. Not sure what brand. Probably any brand is fine (or make your own).
Note that I'm suggesting using stock rubber bumpstops with spacers (NOT buying longer poly bumpstops). Why? Because rubber is softer. Rubber bumpstops are cushier than poly bumpstops. So it's a softer experience when suspension bottoms on a big bump. In the front you get even more cushion from the Metalcloak rubber spacers.