I thought I'd just chime in with my own review of C-IN2 as well. It looks like most of their thongs are manufactured in Thailand.
C-IN2 Core Y-Back Thong
This is possibly C-IN2's signature thong, featuring a Y-Back style very much akin to those from 2(X)IST. This thong is made with a nice cotton blend which felt mostly smooth. I found the front pouch to be an adequate size, not too big nor too small for the package. I like the smoothness of the string back, although prolonged use did give a rather chafing feel on the crotch. Otherwise, I thought the build quality of the thong is very nice, and I very much liked it.
Fit: 5/5
Look: 4.5/5
Comfort: 4/5
Quality 5/5
C-IN2 Active Classic Thong
Unlike the Core Y-Back, this one is made with a perforated polyester blend fabric, for maximum breathability. I really liked the fabric's softness, which is quite incredible to the touch (despite my general aversion to polyester underwear). I really liked the nice thong back, which I found to be a lot more comfortable compared to the Core Y-Back. The front pouch was also quite roomy and nicely sized and fit my package very well. I did take issue with the elasticity of the waistband though since I found it very stiff (more so compared to the Core Y-Back). If it weren't for the stiff elastic band, I would consider this thong to be near perfect.
Fit: 3/5
Look: 5/5
Comfort: 5/5
Quality 5/5