This unit can be installed on a 3" or 4" tongue. I think the description said only 3". It's very beefy and stable and looks better than any wheel jack I've ever had. I've had it on my boat out in the weather for a couple of months now and use it every other day. I have a few minor gripes and one major one. First: The gear ratio is high and if you have a heavy tongue, it will be VERY HARD for you to jack up. Next: The mechanism that locks the swivel has to be jiggled and joggled and sometimes pushed in to get it to lock the wheel up or down. And then my BIG complaint: the actuation of this jack is the least of any wheel jack I've owned which creates a problem if you 1) Tow your rig with different vehicles with different hitch heights 2) Have a VERY heavy tongue and a soft suspension 3) Hitch up on unlevel ground. I've had to put blocks under the wheel, raise, then lower on a block, then raise again to get this thing on my diesel. It might work for you, know it's limitations.
Good, not great. 
