DNA Air Filters - Stage 2 Air Filter Cover Combo for ΚΤΜ Duke 125 / 250 / 390 17-23 - RC 125 / 390 22-23 -Svartpilen 125This new Stage 2 Air Filter features DNAs advanced FCd (Full Contour design) and designed to work exclusively with the DNA stock replacement air filter. Correctly used it willincrease the airflow, torque andpower of the engine. Installation info are included with this new DNA Stage 2 Air Filter. Fuel injection recalibration is suggested but NOT necessary. The filtering efficiency of the assembly with the DNA Stage 1 Air Filter (P KT3N18 0R) is