REI Lightweight Long Underwear Zip Top - Men's

Made of a soft 100% polyester that wicks sweat and dries fast
Tall neck extends coverage; zipper with chin guard lets you adjust ventilation
Flatseam construction, raglan sleeves and side gussets are comfortable as you move
Lower back hem stays tucked in when you lean forward
UPF 35 sun protection
Next-to-skin fit