Sugoi Ready S/S
I grabbed a few of these on SAC and am relatively happy with them. The material and design are really nice, though the fit is way more loose/baggy than athletic. This is an error on Backcountry's part as the Sugoi website has it listed as a relaxed fit.
Also, while it does have flatlock seams in the detailing, there are non-flatlock seams running across the top of each shoulder which seems like a baffling build choice to me as that's the one place you really don't want seams on a shirt like this (please see attached photo of the inside left shoulder for detail). Would probably not recommend for hiking or backpacking for this reason, but it's otherwise a very comfortable shirt.