I went out and looked at the label inside mine, (there's even a serial number!)
Mine is the Small Cruiser and I find it fits my skinny self just fine. The quality is great, mine is about 4 years old now and it holding up very well, just a little sun fading of the cover.
I went for a 150 ride today with only two short stops, my butt was fine until the last 20-30 miles home, I needed to stretch a bit. However, without the Airhawk, I would have been miserable a lot sooner.
The squishy feeling takes a bit to get get used to, but once you do, you realize how well your butt is insulated from road bumps and vibrations. I like that it also sits you up about 1/2" to 3/4" higher (which could be an issue for a shorter rider.)
One thing I should point out is that you want to try to have as little
air in the cushion as possible, just enough so that you're not bottoming out on the original seat. There is a small screw cap valve at the rear of the cushion and it only takes a few puffs of air to fill it up. Then you can play with the firmness until you get it where it works.
But you don't fill these things up tight like an inner tube, it's just enough air to elevate you off the seat. All of the little air pads are interconnected, so the air moves around to form to whatever shape you are and that's where the "squishy" feeling comes from.
Wow, that R model is some bucks! You could almost get two small ones for that much.
Here is mine, again....I love it. Small Cruiser.