I have an Air Head, the only one similar to it is the "Nature's head" almost identical in overall design, a tad cheaper....but consrtuction quality of the "Nature's Head leaves a big gap. Everyone I know who has pucaseedd a Nature's Head either returned it or gave it away and bought an "Air Head". The foot print ismost identical to aa port-i-pottie, but it's 6" taller and more substantial. Quite simply of the composting heads available, the Air Head is the best (about $985). Mine fit perfectly where my portipottie was and the air vent came out just below my Dorade box.
The above statement is bizarre. I have the Nature's Head. It's built like a brick. It could fall off the back of a truck at 50mph and it would probably just bounce. My neighbour has the Airhead. I know a bit about plastics manufacturing and I can tell you the two toilets are made with the identical roto-molded process. They both use all stainless hardware. They are both high quality products. There is no discernible difference in quality between the two brands.
Interesting to note that Channel Cutter Yachts - a builder of very high end Lyle Hess designed 34 footers - installs composting toilets in all boats. He used to use the Airhead, but switched to Nature's Head, because he prefers some of the design features, and the fact that it costs $100 less for basically the same thing.
As I understand it, the owner of Nature's Head used to sell Airheads. But he thought it could be improved. In my opinion, the improvements are insignificant. You could argue the merits of each toilet for an hour, but it's all just splitting hairs.
I know at least 30 people with the Nature's Head, and about 20 people with Airheads. All seem happy. No one has sold one, or gone from one to the other, and no one has given one away.
You can read a review of the Nature's Head on this blog: Nature's Head