This exhaust hose comes standard with models ARP-900E, ARP-900DE, ARP-1200E, and ARP-1200DE NOT WITH THE 1000E or 1000DE. This part can be twisted into the inner adapter (which goes on the back of the air conditioner) and the flat (outer) adapter (which goes on the end of the exhaust hose and into the window spacer) to exhaust the hot air outside. This exhaust hose is 4.5 inches in diameter and can extended 5 feet in length.