The Bullet Proof Diesel BulletProof 6.6L Duramax LML EGR Coolers feature patented H-Core technology, which resists the common causes of EGR cooler failure. The EGR Coolers are engineered for 6.6L Duramax LML applications found in 2011-2016 Chevy and GMC pickups. The H-Core design allows for natural expansion and contraction of cooling tubes inside the EGR cooler, limiting structural failure that can occur at the end of the tubes. The H-Core construction also increases the surface area of the coolant tubes within the EGR coolers, making them more effective heat exchangers than other tubed designs, the company says.