K&N 57-Series intake kits use only non-metallic rotationally molded High Density Polyethylene tubing that reduces air temperature and decrease intake sound over a metal tube. K&N intake kits virtually eliminate air path restriction by replacing the air filter and the entire air path to the engine. The precision engineered tube drives a massive amount of air into an engine, which translates into POWER.
K&N 63-Series Air-Charger intakes are a sister line to the 57-Series and feature the same molded HDPE construction and similar performance gains, but are not CARB exempt, making them illegal for street use in the state of California.