Mountain Hardwear Women's AirMesh Long Sleeve-

Full Product Description (From the manufacturer)

A single layer can have a bigger impact than you think. Our go-to, packable long sleeve houses the highest warmth-to-weight ratio of any fabric in our line, along with high breathability, conveniently comfy thumb loops, and a secure zip chest pocket for stashing essentials. This unique active mesh construction consists of hollow, tube-like fibers that absorb sweat quickly and efficiently supporting insulation and heat-shielding properties to keep you temperature-regulated from the trail to the lift, and everywhere in between.