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.The flow of this new DNA Stage 2 Air Box Filter Cover (TC-Y7N14-S2) combined with the DNA Stage 1 Air Filter (DNA-R-Y7N14-01) is very high, 179.76% more than the Yamaha stock application. DNA S1 & S2 Fcd air filter flow: 171.30 CFM (Cubic feet per minute) @10"H2O corrected @ 25 degrees Celsius. Yamaha stock paper filter: 61.23 CFM (Cubic feet per minute) @10"H2O corrected @ 25 degrees Celsius. Kit doesn't include Stage 1 filter (sold separately).