【4 PCS】Including 4 Oxygen Sensor. 2 upstream sensors and 2 downstream sensors. But they keep the same in appearance and internal construction, which means there is no need to install them in a fixed sequence. 【OEM PART NUMBER】234-4012 234-4018 25312200 25312201 25163079 25165313 25312184 25312200 19178918 19178930 19178937 0258003016 0258986502 0824010008 ES10258-12B1 OZH007 【FITMENT】Compatible with Chevrolet C1500 4.3L 1996-1998, C1500 5.0L 5.7L 1996-1999, K1500 4.3L 1996-1998, K1500 5.0L 5.7L 1996-1999, Silverado 1500 4.3L 4.8L 5.3L 1999-2002, FOR GMC C1500 4.3L 1996-1998, C1500 5.0L 5.7L 1996-1999, K1500 4.3L 1996-1998, K1500 5.0L 5.7L 1996-1999, Sierra 1500 4.3L 4.8L 5.3L 1999-2002,FOR Cadillac Escalade 1999-2000 2002 【PREMIUM PERFORMANCE】Double laser-welded stainless steel body with advanced technology provides high-precision measurement of oxygen partial pressure, precise control of air-fuel ratio and optimized engine performance. 【WARRANTY】1 Year. TAUTOY 234-4012 234-4018 O2 Oxygen Sensor