2000 SR Ducting is specifically engineered to handle unconditioned air. The 2000 SR Series can withstand high heat, high humidity and excessive CFMs without any failure or fatigue. 2000 SR features a triple laminate with industrial grade foil casing for durability, and an ultra-smooth double sealed core for frictionless and silent air flow. The "Carbon Black" inner core does not reflect light. "Rip-stop" prevents tearing, galvanized spring steel maintains duct shape and prevents rust. The SR series is c-ETL-us certification tested and verified to conform to UL181 standards. Also available in custom lengths.