The Peterbilt 3S Flex Exhaust Bellow is designed for OEM Numbers M66-6559 and KW-6559. This exhaust bellow features a natural finish and is sold individually. It fits most Peterbilt models and is compatible with both OEM and aftermarket numbers, including M66-6559, KW-6559, M666559, KW6559, 58538, 58538KIT, and 58538-KIT. With its practical design and wide compatibility, this exhaust bellow offers a reliable solution for your Peterbilt vehicle's exhaust system needs.