Used in conjunction with the 4 inch round 3M™ Fire Barrier Pass-Through Device, these 3M™ Fire Barrier Pass-Through Single Mounting Brackets PT4RMB provide additional support to the device.3M Fire Barrier Pass-Through Single Mounting Brackets PT4RMB come with a pair of brackets (includes bracketing screws) for mounting on both sides of an assembly. 3M Fire Barrier Pass-Through Devices use a unique fixed fire-rated intumescent material which works in conjunction with a foam smoke seal and optional mounting brackets. In the event of a fire, intumescent material quickly expands to seal the inside of the device, helping to prevent the spread of smoke and fire into other compartments. Optional mounting brackets and additional foam smoke seal replacements (device comes with 2 foam seals) sold separately. Square devices can be stacked in multiple device configurations for larger cable management and firestop requirements.