I am not sure this will be helpful as I see it is out of stock now but......Perhaps will be restocked?
In any case a very fine lightweight LS base layer. I find it has a wide temp range & use it from 45-75 degrees no problems.
It is nicely fit & does no bunch up anywhere. When cold it feels good & nicely warm yet when it heats up it feels nicely cool lifting sweat away from skin
Overall very nice & wide range of temp usage
I am a 37" chest 146lbs 5'8" & the Medium fits nicely. I may have been ok with the Small too but med is fine