Mons Royale Olympus 3.0 Long Sleeve - Men's: Our warmest baselayer is a cold-weather classic. The slim fit 250 merino will keep you warm, while breathable mesh panels prevent you over heating. Detail Mons 250 merino wool, our warmest baselayer weight Slim fit and raglan sleeves for ease of movement Merino mesh underarm panels Thumb loops to lock out the cold. Fabric composition Merino Single Jersey 97% Merino Wool 3% Elastane Weight 250gsm