I was able to order the Inov-8 3mm insoles (footbed) from Zappos last week. They arrived today. I have not yet run in them. I have one pair of grey/red and one pair of blue/green. Zappos calls them black/red and blue/lime. I will call them Red and Blue, below.
On Zappos, you get the idea that only the color is different. But that is not correct. The length and heel-width is the same. Both have a molded heel cup. But the Blue is 5 mm wider in the forefoot. When I line up the heel and midfoot, the extra width is on the outside of the forefoot.
The Blue is flat in the midfoot arch section, while the Red has a pronounced molded arch. And neither pair is 0-drop.
There are ventilation holes all over the insoles, so I used a paperclip to probe the thickness. The heels of both the Red and Blue insoles are clearly thicker than the forefoot. The forefoot on both is 3 mm as advertised, but my inexact paperclip probe shows about 4 mm in the heel. Maybe 4.5 mm. I was able to use a ruler to measure the thickness of the forefoot, but the paperclip was used to get the difference in thickness between heel and forefoot. I would have to cut the insole down the middle to use the ruler on the heel, and I am not ready to destroy the insole.
Also, the holes on the Blue are uniform diameter over the insole. On the Red, the holes are more widely spaced. They are about the same size as the Blue on the forefoot, but become about double in diameter at the heel and mid-foot.
Using the finger-squeeze test, the heel of the Red feels softer than the heel of the Blue. That may be caused by the larger holes, or maybe the foam is different.
I can't find Pete's blog post on these insoles to compare with his comments.
Your mileage may vary,