This manifold is cast from 347SS which is far superior to 304SS. Not only does 347SS last longer at elevated temperatures , there are no welds like those found in traditional turbo manifolds. When a welded turbo manifolds fails, they almost always break at or next to the welds. A broken turbo manifold even if it features a life-time warranty can be a serious hassle to remove and send back in for repair, especially if you miss a race because of it. We have weighed our cast manifolds vs our welded units and they actually weigh a few ounces less! Since these manifolds are investment cast, they are less than 1/2 the thickness of your traditional cast iron turbo manifolds, and therefore do not retain as much heat as cast iron manifolds. There arezerodownsides to this casting process vs welding. Tapered Main Runner Inside Diameter This manifold's inside diameter slowly tapers down as it reaches the T4 flange. This process is only possible with a cast manifold. A traditional welded manifold does not change inside diameter. This tapering process is identical to the volute of a turbine housing. By tapering down it increasing velocity, and speeds up the exhaust flow and increases boost response. CNC machined flanges All flanges are CNC machined to be perfectly flat. Most turbo manifolds are just belt sanded flat, which is not as accurate as CNC machining. Smoother transitions Welded turbo manifolds require hours of hand porting with a die grinder, and sanding drums to contour the change in shape from a round tube to a square T4 flange. We have taken this step, just like the rest of the manifold, to an even higher level of quality. The investment castingprocess makes every transition seamless. Welded manifolds are made from short pieces of cast elbows. Every time there is a joint it is welded, there can be a slight disruption on the inside diameter if the pipe is not perfectly matched, or the weld penetrates all the way through. This disruption is eliminated with the casting process resulting in a better flowing turbo manifold.