midweight “polar” layers never really worked for us. they got cozy right but we wanted cozy and “really fricken breathable” for our below zero sunday long runs. COOLmatic | EXP™ DIAMAfleece anchors the performance via a lightweight diamond grid of recycled polyester pile for warmth. imbedded carbon pushes temperature control to another level. the diamond grid, allows for maximum breathability as well as extra weight reduction. we added two way half zip for customized ventilation and versatility. reflective details. outer phone pocket to keep your hands free. oh, speaking of hands. check the cuffs and get back to us (seriously, have a look). engineered for the inevitable temperature drops, built to keep all of us outside and comfortable no matter what jack frost throws our way.