There are several types of aluminum pipes, including seamless pipes, extruded pipes, and welded pipes. Seamless pipes are made from a single piece of aluminum and have no welds, making them the strongest and most durable type of aluminum pipe. Extruded pipes are made by forcing aluminum through a die, which gives them a uniform shape and thickness. Welded pipes are made by welding together two or more pieces of aluminum, which makes them less strong than seamless pipes but more versatile.