Product Features:High quality rolling metal fire doors with insulated metal backOptional internal flame baffle prevents infiltration through headerApproved for roll down stainless steel fire doorsOversize UL label up to 56′x30′Overhead fire rated doors are built in accordance with the requirements specified by Underwriters Laboratories Inc.Functional BenefitsThese insulated rolling fire doors provide access control and security protection under normal use and will close automatically in the event of a fire serving as fire stopping to contain the spread of a fireEliminates all mechanical fire gears on the brackets and the need to reset spring tension3 hr Rating – 3 hour approved for doors in dividing fire walls 1-1/2 hr Rating – 1.5 hour approved for doors, in vertical shaft openings3/4 hr Rating – 0.75 hour approved for doors in a corridor or a room-partition4 Hour Rated (Optional) – Consult factory for more informationFire rated doors over 152 square feet will receive a Classified UL label marked “OVERSIZE ROLLING STEEL FIRE DOOR” that includes the hourly rating as well as the certification number