The  medicine cabinet was mounted into the wall. The opening required for this unit is a little smaller that other 20"x26" unit it replaced but can be easily retrofitted. This is    from smaller flanges that hide the mounting opening than  my previous unit. Besides the mirrored outside, this unit also has mirrored glass on the inside on the door as well as indide the unit as well. It is also fully alluminium so there should be no rust like the previous  unit.