I just got the 60mm version. Feels high quality overall. A slight burr or coating buildup that could dig into the handlebar that I'll deburr. I'll grab some pics when I get it on a bike. I was originally thinking of just using it to do a bike fit, then ordering either a real Syntace FlatForce or integrated bar/stem, but I'm thinking I'll use the ZTTO.
One thing to note is that I've read the Syntace stem measures longer than it's supposed to be, I think that they measure perpendicular to the steering axis (thus center of steerer tube mount to center of handlebar is longer than the length states). The ZTTO stem appears to be measured the traditional way, a true 60mm stem with -20deg slope.
The stack height is only 28mm, so great for short steerer tubes, or putting used forks in big bikes with long head tubes.