Thanks for that, I've actually read that standard and it regulates the face dimensions but not the depth. A NEMA representative suggested using GFCIs, etc as a guideline but as far as percentage of box thast can be filled or back clearance, it seems is not regulated.
Is there a standard on dimensions of a duplex receptacle on a single yoke? We are looking to manufacture an additional circuit to be added to the back of a standard 5-15 outlet which would give us wireless control over it. According to the NEC and NEMA the receptacle counts as 2 conductors...