What kind of fabric is this?

Maybe their 'Regulator' grid fleece?

There's no grid inside of the shirt like the R1.

I thought maybe you just wore it the grid out.

Nope, it's been this way ever since I bought it. Thanks though!

If I can figure out what this is, it might quench my desire to buy an R1 or something comparable.

Looking online, I'm guessing its Cap 3…but not sure since I don't have a Cap 3 shirt to compare it to.

Looks like an older style cap3

I have this exact item. It's Cap3 for sure.

I have a 1/4 zip Cap 3, long sleeve, in black that looks about the same. I'd say 2009 Cap 3.

If there is a tag near the lower left with the care tag and you can read "style" numbers, we may be able to track that.

Hard to read, but style 26651S0 = Lightweight Sun Hoody, Summer 2010

Another version, 84700FA11 = Down Sweater Full Zip Hoody, Fall 2011.
See http://www.patagonia.com/us/product/mens-down-sweater-full-zip-hoody?p=84700-0-331

Older tags can be much smaller and very plain without all the Patagonia stuff on the tag, just "cut" and "style" and country of manufacture. I was identifying a Capilene zip top I got for my daughter and could just make out "44274" and found this web page with a ton of info: http://www.tetongravity.com/forums/archive/index.php?t-24345.html So I have a Capilene mid weight top

Trailspace.com is a very good resource for identifying gear.

I would love to get set of swatches with all the Patagonia fabrics. Patagonia is actually pretty easy if you have the tag number. The ones that make me crazy are the older Outdoor Research items. They have cranked out so many items over the years. I'll bet they have marketed a couple hundred hat models. The new ones have an actual model name on a tag– if you're lucky.

Dale, your first picture is close, but my fabric has more of a cross-hatched pattern instead of a rectangular hole pattern (for lack of better words).

I looked at the tag, and this is the info I have – RN: 51884, CUT: 41546, STY: 44440F8 <—that's a zero before the F, not an O

And two other sets of numbers with no identifying text: 888052763766 and 0467238961

Anyway, I've had no luck on trailspace or google. It insulates really well, so I think it might be Cap 3, but if someone is able to use this info to find out for sure, that would be cool.

Search "Patagonia 44440" on Google. It's Cap 3 made in Fall 2008. Thanks to Dale for the lesson in reading their labels.

Thanks Peter! Didn't think to only put the digits.

I concur!

http://reviews.patagonia.com/9248/44440/reviews.htm

Back when I sold auto parts, I used to say, "if I can't find it, there are only two reasons: it doesn't exist, or you really didn't need it in the first place!"