The Men's Stay Cool Sleeveless X-Form Compression V-Neck (CO10X) was specifically designed for the high endurance athlete. The STAY COOL fabric has been engineered to decrease your skin's surface temperature up to 10℉. The STAY COOL Long Sleeve Compression Top contributes to the compression of the core through the shoulder, allowing superior range of upper arm motion and eliminates any core restrictions. The Biomechanical X-Form design reinforces posterior muscles, and also combats fatigue by promoting good posture and form while in motion. The Biomechanical X-Form construction is constructed with a 0.3 mm NeoSkin that reaches from the middle back to across the shoulder with an inner fabric lining for comfort.