UPF 50+ Eclipse Sun Sleeves feature high performance 37.5 fabric technology. This higher performance fabric offers unrivaled sun protection, moisture control and cooling. The sleeves are designed to cover the back of the hands, which are particularly vulnerable to sun exposure. They stay up your arm by virtue of the spandex component (87% Cocona/13% spandex) so even a vigorous golf swing won't cause them to sag. Zero-distraction fit under golf and cycling gloves, or roll the hand covering up to the wrist. The stretchy fabric allows a lot of latitude in sizing, so if your style is active, consider a smaller size for a more snug fit.