Each hidden breather is O-ringed at the heads and exits at the mouth of the injector/carb to provide efficient engine breathing, eliminating the need for any external hoses or hardware Standard red filters are pre-oiled, washable and feature four layers of surgical grade cotton for optimum filtration and maximum airflow Radius air inlet provides maximum performance by providing unobstructed airflow One-piece aluminum backing plate features hidden breather technology All necessary hardware and instructions are included with each kit. BIG SUCKER STG1 99-17 NAT