Don't think because you might not have heard of ZERO RH+ that this base layer isn't worth it. It is really nice. Why? It is an engineered knit piece..basically it is made to contour your body by varying the thickness of the material with out a seam present. This top fits like your favorite sock & wicks moisture away from your skin like crazy. I am 5'11" and I wear a large as painted on tight to allow for maximum moisture transfer. Roll in this with a ZERO RH+ jacket and enjoy rides in temperatures that you never thought were enjoyable.