The Mullion Rail is an OEM part for Bosch refrigerators. This part maintains an effective seal on the refrigerator door, helping to keep cold air inside and ensuring energy efficiency. The mullion rail folds when the door is opened and extends to create a tight seal when the door is closed, preventing air leakage and maintaining consistent internal temperatures. Causes of a bad Mullion Rail can include wear and tear from frequent use, mechanical damage from forceful handling of the refrigerator door, or degradation of the rubber seals that can compromise its effectiveness. Symptoms of a failing Mullion Rail include: Difficulty in closing the refrigerator door fully. Noticeable gaps or looseness around the door seal area. Increased condensation or frost buildup near the door edges. Escaping cold air from the refrigerator, leading to increased energy usage. This OEM Bosch part is also compatible with Thermador, Gaggenau, and some Kenmore models.12722815B (AP4456332) replaces 1541326, AH2365248, EA2365248, PS2365248.