What is NOT a common size for galvanized sheet metal electrical outlet boxes?

The dimension that is not a common size for galvanized sheet metal electrical outlet boxes is 4" X 1". Standard electrical outlet boxes are designed to accommodate various wiring configurations and devices, and these typically require a greater depth than what a 1-inch dimension would provide. The other dimensions, such as 4" X 4", 4" X 2 1/2", and 4" X 3", are established sizes in the industry, allowing for necessary space to contain wiring and devices while maintaining code compliance and safety. The shallow depth represented in the chosen answer would not meet the functional and safety requirements for electrical installations.