Forged billet aluminum backing plate features Big SuckerÖ hidden breather technology and a radius air inlet for smooth airflow Forged billet air filter covers feature exposed design and a CNC inverted top that acts as a velocity stack to help pull in more air flow Hidden breathers are O-ringed at the heads and exits at throttle body/carb to create a virtually closed-loop system Performance filters features a black synthetic filter element wrapped in a stainless steel jacket Black stainless steel jacketed inverted filters feature an inverted pleated top and 360? of pleated sides to pull in filtered air from every angle CNC-machined from forged billet aluminum No external hoses or hardware needed Made in the U.S.A.. AIR CLN S-TRCK 91-19XL BL