This super light and casual button-down features UPF 40 sun protection, sweat-wicking tech and venting—making for an easy go-anywhere, wear-anytime shirt. It packs a powerful combination of our Omni-Shade UV-blocking coverage and Omni-Wick performance wicking. A mesh-lined vented back adds breezy comfort. Columbia offers this short sleeve in multiple colors and sizes. Extended sizing available. Regular Fit. To ensure the size you choose is right, utilize our sizing chart and the following measurement instructions: To determine the neck size, measure at the base or thickest part of your neck. For the chest, measure at the fullest part of the chest, under the armpits, and over the shoulder blades, keeping the tape measure firm and level.