No they are not made of sinks as they would be way too heavy for packing in.
Its 300 deep x 250 wide x 250 high
Sinks would be great for one to use from a vehicle where weight wasn't an issue.
Same sort of arrangement with the addition of a solid alloy sheet base bigger than the fire box for the legs to attach to. As a heat shield underneath and ash tray.
I will be making a sink based one soon because I have just spent 3 days in the Canterbury high country staying in a private musters hut you can drive to.
All the open fires were hopeless as a little of your front got mildly warm and there was -3 degrees air being drawn into the hut and whistling past you and taking all the heat up the chimney.
So a nice big sink model with a couple of elbows in the flue could have sat just in front of the hearth and maybe actually put some heat into the room.
To be fair it was probably the coldest few days of the year up there so far. Even the station managers wife was complaining about the temperature !