The short-sleeve version of Castelli's Prosecco Tech Base Layer line follows the layout of its longer-sleeved sibling and uses a simple blend of fabrics to elevate your riding comfort in cool conditions. The short-sleeve Tech warms the core on rides from 50-68 degrees F using a proprietary stretch knit on the main body for insulation, and a PrimaLoft fabric on the waist and back. This combination Castelli claim offers essential thermal mapping to give warmth on the chest and arms that take front wind while reducing heat buildup where the Tech is tucked into bibs and where the bib straps already provide a layer of warmth. It's a very thoughtful bit of construction in a garment that most of us probably consider as a basic layer. Castelli adds Prosecco hydrophilic treatment to the Tech for maximum wicking under heavy sweating. And the crew neck sits close and wide to conceal out of the way of a jersey collar.