The Invidia header for the Honda Civic Si is made of high quality polished stainless steel to enhance the beauty of your engine bay as well as provide a significant power gain all throughout the powerband. This Invidia piece is a 4-2-1 design to boost low end and mid range torque. A built in flex pipe prevents cracking allowing to last the life of your Civic Si. Invidia has seen power gains of 20 horsepower and 11 ft/lbs of torque.