I guess it could be for any size boat over 12' long.
I got some Awning struts after a Tornado came through here.
From some Roller Blades, I got some nice durable Rubber (quiet) wheels with Roller Bearings inside. That's important, because you want this thing to be drag free.
From the Barn I got an old Lazy Susan for Boat seats. I mounted that Metal part on a couple of Axles made of 'allthread' and put that Carriage inside two lengths of Awning strut.
Perfect those wheels just fit perfect!
My Grand Daughter says she'll have none of this unless her Hairy Legged Sinner (Boyfriend) takes a notion to go fishing.