Are these inserts worth buying? I have Danner Fort Lewis boots but no Airthotic inserts. My heels are a tiny bit loose while thr rest of the feet fit fine.
Who has tried Danner boots with and without the Airthotics? Or, for that matter, tried them in other boots?

I can't speak to the Airthotics, but I use Superfeet and SOL Insoles. The Superfeet made a huge difference in my overall comfort. SOL's are heat moldable and have truly moved my comfort level to a whole new world.

I have very tall arches, which resulted in brutal blisters even after just a couple of hours of hiking. Add Superfeet and I was up to 12 hour days. Add the SOL's and my feet are in heaven.

YMMV.

Good question. I got them with my pair of Danner hunting boots years ago, and found they do little to improve cushioning or support, but they do manage to keep your heel planted squarely in the back of the boot. I stopped using them in my hunting boots because they kept having a tendency to slip forward and throw my step out of whack. I've found other uses for them in my casual footwear, as they seem to provide a little extra support in what would otherwise be shoes that were too soft. I don't think I'd spend the $$ on them; you may be better suited by a pair of dedicated full-length insoles.

I have them in every pair of boots I own. I have probably the flattest feet ever seen. I use the airthotics with a set of Spenco insoles and my Danner Quarry's and Quarry 2's have never been more comfortable. The boots that really benefit from them are my Danner Frontiers. Right now with the airthotic and insole they are the most comfortable thing I have. They are more comfortably than any pair of shoes I own.

I'm not sure about any of the "high tech" boot stuff...

I was recently overjoyed to find a surplus store that had
a supply of "old stock" felt liners for my Sorel Pathfinder PAC boots.

I'm kicking myself for only buying two sets, but I didn't have the boots with me at the time.

AD