If it's like my 19RD, 3/4".
But My trailer came with a speed handle, kind of like a bit brace with the correct socket welded on.
You could write a book on what is not in the manual, not mentioned by the salesperson and not gone over during the PDI!
How big are the tanks, what size are the lug nuts, where is the spare tire, power rating on the microwave, why doesn't the fan settings on the thermostat make any sense whatsoever, how do you purge the gas line to the water heater, what is the correct for the BBQ connector, ....
Give yourself a year of using the RV before the questions start to calm down.
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!