NBS= New Body Style (Does not look like my truck in my signature) The new Silverado/SierraRCSB = Regular Cab with a short bed (5'8). ACTUALLY a RCSB is a Regular Cab Short Bed truck with a 6.5 ft bed. See mine below. Also: GMT800 = 99-07 style trucks. GMT900 = 07 up new body trucks. There are more.