From Lloyd Industries, Inc. (Montgomeryville, PA), the MDL-FSD-111 is rated at 11/2 hour for 2-hour rated partitions and has leakage ratings of Class 1, 2, 3, and 4. The blade seals and jamb are made of stainless steel, and the bearings are sintered bronze. A high-tension spring closes the damper positively, and the linkage is protected and concealed in the channel frame. The construction allows complete blade closure even in high-temperature environments where metal expansion occurs, according to the manufacturer. The MDL-FSD-111 is available in various sleeve and actuator options to satisfy most applications.