Banks Power 17-19 Chevy/GMC 2500HD/3500HD Diesel 6.6L Boost Tube Upgrade Kit - RedBanks massive 3. 5in boost tubes are the largest charge air cooler pipes on the market, flowing 680 CFM and 87% more air than stock! Smooth mandrel bent tubes deliver more air to your engine while reducing boost pressure loss resulting in quicker turbo spool and more power. Key Features: Huge increase in size and flow over stock and competitors (3. 5" vs 2. 5"), Billet venturi couplers maintain boost pressure, Mandrel bent aluminized steel