Merino wool is classified as a micron at a certain level (diameter), however, the finer the microns of the merino wool the softer it is next to skin because the thinner and finer the wool.
For instance (next to skin base):
KUIU uses an 18.5 Micron wool
FIRST LITE uses 17.5 Micron wool
SITKA uses 18.9 Micron wool
An industry standard for "MERINO" is wool having a micron measure of 18-24 microns. A MICRON is one millionth of a meter. While 18-24 microns is the "industry recognized standard" merino wool can be finer than 18 as FIRST LITE is using.
How do people feel about exoffio or redram boxers and long underwear? I get discounts when ordering from the manufactueres themeselves and first lite and minus 33 my top two choices are out of stock and dont seem to be getting anything anytime soon.
Started making the slow shift from polypro last year after getting tired of the damp cold feeling after movements to camp; this after years of using poly. I have the KUIU 185 baselayer top and I think it's my favorite piece of kit. I will spring for the 185 bottoms soon! I also get a good deal from First Lite but like you, the inventory I have access to is a bit slim. Hence KUIU...
I had been wondering the same thing, on the differences between the different Merino Wools. I've been reading it is a two part equation between the quality of the fiber, quality of the spun yarn, and quality of the way the fabric is produced with the machine settings and a host of other factors. I found a write up on the subject a bit on the REI site,
The quality of the wool fibers are judged by their thickness in microns. The thinner the raw fibers, the softer the wool. Merino wool fibers range between 15 to 24 microns in diameter, with 17.5-micron fibers (rated "ultrafine") often used for next-to-skin apparel. The merino industry regards 18.5 microns as the average fiber diameter most people can wear without experiencing an itchy sensation.
The link I posted above it the article I wrote on Merino Wool. Its a short read approx. 800 words but at the bottom I have cited a few links to check out. The wool.com website is the Australian Merino Wool main site. You want tons of info on Merino Wool and there is your place to get SOLID answers over manufacturers websites, IMO.
Go deeper, stay longer, smell yourself less --- Merino Wool