Castelli's Most Versatile WarmerOther Warmers on the market are made with a nylon/Lycra blend that tends to hold moisture, but Castelli knew they could get better moisture management with a polyester yarn. Working with polyester makes it more difficult to get the right stretch, return and manufacturing consistency, though. These Castelli Pro Seamless 2 Arm Warmers are a pro rider favourite because they're crazy light and they're extremely warm for their weight, yet even in milder conditions you don't overheat. They're so stretchy you hardly feel them on, yet when you take them off they occupy a fraction of the space that normal warmers would take in your pocket.