The frame on my 2015 (Pre Thor by about two weeks) 329ik has an I beam frame. It has the name of a steel company and USA stamped into the I beam. It also has two 5200 lb axles and only a 9500lb GVW. That is my biggest gripe with mine, the lack of carrying capacity. All those nice cabinets and we have to be real picky about what we put in it. It should have a 10k lb GVW, IMO. Otherwise we are very with ours. Just over a year old and 6000 miles in ours.