Most of us use long-sleeve jerseys for a few days in the spring and fall, then extend their range with a vest in cooler weather, and then pull them back out for insulation duty under a jacket in extreme cold. So a thermal jersey shouldn't be too bulky or complicated, yet you don't want boring. We built this with all the essential features, like great fabric and fit, perfect pockets, and our lightweight easy-sliding YKK Vislon zipper.