Ruskin - The FSD36 Combination Fire/Smoke Damper is both UL555 and UL555S Classified, rated as a 1.5 hour fire damper and a Leakage Class II Smoke damper https://bddy.me/33mSEMK | Facebook
Ruskin Authority in Air Control, Fire / Smoke Dampers and Louvers
CD36CE : Critical Environment Damper: 316 Stainless Steel, Rectangular, V-Groove, Class II Leakage, Medium Duty, 3000 FPM, 5" w.c. Max