This S2 Air Box Filter Cover features DNA's advanced FCd (Full Contour design). Installation info are included with this new DNA Stage 2. A specially made Laser cut supporting frame is included with the DNA filter. The filtering efficiency is extremely high at 98-99% filtering efficiency (ISO 5011), with 4 layers of DNA Cotton. This DNA filter is designed as a High flow Air filter for:'Road & Race use'. The DNA Stage 2 Kit, can be either a DNA filter or a DNA cover that is designed to replace a part of the air box, seriously increasing air flow to the engine. With the proper fuel recalibration the results are always very impressive.