The KRP-250 is non-insulated and rated by Underwriters Laboratories for 1.5 hour "B" label in walls, and may be used in 2 hour fire rated wall assembly. Karp Non-Insulated Fire Rated Access Door for Walls Only KRP-250FR The KRP-250 FR is non-insulated and rated by Underwriters Laboratories for 1.5 hours "B" label in walls, and may be used in a 2...