B Series Bisi Style Header V2 4-1 Merge Collector B18 B20

B-Series header features a true 4-1 merge collector for more equal exhaust flow. This header delivers the best peak horsepower gains while utilizing a 2-piece design. This is ideal for all forms of competition; Autocross, Drag racing and road racing. Recommended for 1.8L - 2.0L engine displacements. Made of 304 Brushed Stainless steel True 2.65 (ID)inch collector outlet Hand TIG Welded CNC-ed machined manifold flange One year warranty 18G on the 304 S/S. Measured at .049" to .050" OEM spec header gasket OEM spec donut gasket  Two piece design Half core radiator must be used