Markr1234 answered the question I had too: I was confused because the 6-20P receptacle will accommodate up to 10 gauge wire, but the plastic gang box that comes in the installation kit (EVK02) has strain relief openings for only 12 or 14 gauge.

But here's what I don't understand: supposedly #12 copper conductors can only handle 9.3 amps: http://www.powerstream.com/Wire_Size.htm So why is #12 wire OK when the EVB22 is spec'd to 16 amps? I'm sure your answer, above is correct and I am going to use #12 wire: I just want to understand this contradiction for my own understanding. thanks!