When it comes to base layers, you deserve a versatile layer that works as hard and often as you do. The year-round Merino 150 Base Layer Short Sleeve can challenge any climate with the body temperature regulating properties and breathability of Merino. Featuring Core Spun technology, they’ve wrapped Merino around a nylon core for added strength, without downgrading on comfort. they added smooth flatlock seams to minimize chafing and eliminated shoulder and side seams so you and your pack can move with ease.