Our arm sleeves are designed to protect your arms from the sunlight (block solar radiation). 1 Pair/Set of Certified UPF 50+ Sun Protection (Blocks 99%+ of The Sun's harmful UVA/UVB Rays). They are made of elastic micro fiber that allow maximum breathability, 90% polyester 10% spandex. The Fabric was designed to wick (draw humidity away from the body and expel it). No fade or lose elasticity.