[Vehicle Fitment]: Compatible with Chevrolet Express 3500 2003-2004, Monte Carlo 2006, Silverado 1500 2000-2005, Silverado 1500 HD Classic/Silverado 2500 HD/Silverado 3500 HD 2007, SSR 2003-2004, Tahoe 2006; Compatible with GMC Savana 1500/2500/3500 2003-2005, Sierra 1500 HD Classic/Sierra 2500 HD/Sierra 3500 Classic/Sierra 3500 HD 2007---Fit Square Coil only, Not fit Round Coil; 10.2mm Spiral Wound Design; Fit V8 only. [Reference Number]: The A-Premium Ignition Coils and Spark Plugs Kit's reference number: 48322R, UF-271, 12558693, 3859078, 50253, 521618, 5C1083, E226, H6T55171ZC, 26347, C561, UF271. Before placing an order, verify that the part is compatible with your vehicle using the compatibility system.. [Iridium spark plug]: Iridium is a type of refined alloy which is highly suitable to be used as the materials of the central electrode in a spark plug. It extends the life of the spark plug nearly threefold, ensures a more stable idle speed of the engine, and delivers a super performance to the engine with improved fuel efficiency, reduced emissions and faster starting up..
