aFe 01-04 GM V8-6.6L LB7 Twisted Steel Manifold w/ Up PipeConstruction: These unique up pipes are constructed of 2" mandrel bent 304 stainless steel tubing with a . 120" wall for strength and durability. 2" Inner Liner Flex Pipes: The down pipes utilizes heavy duty 2" flex tubes with internal inner liner. Leak Free Seal: High quality 3 8" thick flanges are used for a complete 360 degree sealing surface. Machined Ports: These manifolds have both the inlet and the outlet ports machined to match the factory