The most crucial feature of sun protection arm sleeves is their ability to block ultraviolet (UV) rays. They are typically made from fabrics with a high Ultraviolet Protection Factor (UPF), often rated UPF 50+ or even higher in some premium models. This means that these sleeves can absorb or reflect a significant amount of the sun's UV radiation, reducing the risk of sunburn, premature skin aging, and potential skin damage on the arms. Whether you're out in the sun for a short stroll or engaging in prolonged outdoor activities like hiking, cycling, or playing sports, these sleeves provide reliable protection for your skin.