Sold as each. 4". Aluminum skinny duct with round take-off adjusts from 27" to 48". Oval duct allows for dryer venting installation as little as 3" from wall can be cut with tin snips to shorter lengths. 4" round take-off accepts other duct for longer installations. Ideal for basement installation. Manufacturer's number: DAF3. Buy Hardware Supplies SKU #: 4165122. Country of origin: Canada. Distributed by Deflect-O.