The two pictured skid plates primarily protect the front differential, engine, transmission areas. There is a third, smaller skid plate that bolts to the crossmember that protects the transfer case.
I bought the front two from the seller mentioned above, and the transfer case one from another eBay seller.
GM Offers all three as a kit as well, which comes with all the bolts. I don't have the part number at the moment.
I just ordered these two, if you have the part number laying around for smaller one that would be awesome
thanks
P.S those bolts are kinda pricey lol