Hogpaw, I forget how many inches it measures, but I've got one of
the ones from Cabelas with the float/weights built in - it is a XL size.
It works good on my 18' Al boat, there are times I wish it were a little
more effective, but it is only when it is really howling - I'm talking whitecaps
slopping over the transom. I think instead of going bigger, I may just get
another one the same size, pull two when I need more "brakes".