One other thing to clarify is that PS=pro stock, SS=super stock, and K boat are all the same hulls and manufacturers. A flatbottom design of typically 18' in length. They use the same hardware and all run 5 mile races. (usually four laps) The flatbottom boats usually start their race while running, they pair up for a flag start. The GN=Grand Nationals run an endurance race that usually start from the beach on a timed countdown. This comes after a few laps of warming up in seeming chaos. They run about five times as long of a race as the flats do. They have a v-bottom design and usually run around 19-21 feet long.