If you are installing then that circuit breaker needs to be a single pole type.. Like the 15 amp breakers in your box. What make depends on your breaker box (Same as the rest of them) so only you can answer that. But make sure it is a single breaker, NOT two breakers ganged together (120 volt, not 240 volt)
Someone ask why 4ga wire, Yes, 4ga is a bit heavier *I would likely use 8) but the heavier the wire the lower the line loss
I would install 4-wire lead (l-1, l-2, Neutral and Ground) tape off one of the L lines.. THat way if you ever want to upgrade to 50 amps, Just untape, repalce breaker with what is now the WRONG type, and change the outlet.
or better yet, Go 50 now and use a dogbone for 30 amps. You can use 30 amnp breakers if you like with 50 amp outlets,, Just label the outlet "30 amps"
