This part comes standard with models ARP-900E, ARP-900DE, ARP-1000E, ARP-1000DE, ARP-1200E, and ARP-1200DE. This part connects to the end of the exhaust hose (ACK09135) and snaps into the extendable window spacer (ACK09601). This adapter is compatible with 4.5" and 5" diameter exhaust hose. It has a oval shape on the end where the window panel snaps on to. (L: 8-1/4 inches, W: 2-5/8 inches)