Oops your correct. Attached the wrong pictures. RV is round center pin and six flats on the outer.

 

I'd just like to know how we've come to have so bloody many different trailer plugs. The flat 4 is self explanatory. The flat 5 comes to us courtesy (primarily) of the boating industry. Then we have round 5,6 and 7, plus 7-way RV. Then to really ice the cake there is round 9 which was used for a while in the RV industry (back in the 80's) for RV's with 3-way refrigerators that ran on 12V while towing. They had a second dedicated 12v line to the fridge along with a switched ign. wire to tell the fridge when the tow vehicle was running, and subsequently switch over to 12v mode.... whew.
I've been wiring trailers since the late 70's and I'm glad to see some standardization happen. I'd be all too happy to see everything get a 7-way RV and be done with it. So what if there are unused pin locations in the plug? Anyway, cheers!