REI Midweight Long Underwear Half-Zip Shirt for $16.83. Select in-store pickup at REI to save on shipping. Otherwise shipping is free on orders over $50. If needed, use this Filler Tool to qualify for free shipping. Here is a screenshot for reference. The shirt is made of 4-way-stretch polyester fabric with nonchafing flatseam construction, and has a front zip, and UPF 50+ sun protection rating.