The arm length and how well it washed and it it surprised me being warm!This is a unique layering piece you’ll want in your cold-weather cycling arsenal. I wear a merino wool base layer and make this sweater my next layer. The merino layer wicks moisture, this layer (100% synthetic) further wicks the moisture into your jacket liner, the venting at the armpits enables just enough cooling to mitigate moisture, and the turtle neck keeps your neck warm and extends up over your chin and mouth on colder days. Rated this only four stars because it feels a bit flimsy in terms of construction, but so far after multiple washings, it’s held up well.These are my new favorite for cold weather cycling. I wear this with a winter cycling jacket, and all is well. Only complaint would be that they run a size small, so be prepared to size up for a good fit.Wore this out for a cycle and it's Awesome!! the turtle neck bit can fold up to cover your mouth for extra cover. material is nice and high quality! Would recommend for the colder rides out!Produkt erfüllt die Erwartungen als Baselayer für winterliche Fahrradausfahrten. Was jedoch zu bemängeln ist, ist die Länge des Unterhemds. Der Artikel ist viel zu kprz geraten, um den Nierenbereich zuverlässig vor Kälte schützen zu können. Hier ist am Design dringend Nacharbeit angesagt, zumal Castelli einen entsprechend hohen Preis verlangt.