4pcs 2 Upstream & 2 Downstream Oxygen Sensor 1 Sensor 2 Bank 1 Bank 2 Replacement for 2008 2009 Chevrolet Silverado 1500, 2008 2009 Chevrolet Silverado 2500 HD, 2011 GMC Sierra 2500 HD Upstream length 450 mm (17.71"), downstream length 450mm ( 17.7"). 2*Upstream & 2*Downstream Oxygen Sensor. Wires: 4 Direct Plug-In Replacement. Warranty: One year unlimited miles. Please check fitment before purchase.