Baleaf Men's Short Sleeve Running Fitness Workout Compression Base Layer Shirt 88% Polyester/12% Elastane Breathable, soft and moisture-wicking fabric keeps you dry and comfortable Stretchy and durable material grabs your muscles tightly and improves your performance 4-Needles Flat-seams minimize irritation caused by chafing Ergonomic compression fit for enhanced range of motion Please order ONE SIZE UP for a regular fit; Order usual size for a compression fit