Introducing the Adjustable Resistance Training Mask—your essential silicone gear for high altitude simulation during cardio, running, cycling, and fitness workouts. This mask enhances breathing, strengthens your diaphragm, and increases stamina while providing allergy and pollution protection. With 4 customizable resistance levels, you can adjust airflow intensity in real-time. Made from lightweight silicone with breathable mesh and strong Velcro for a secure fit, it's perfect for various sports. Enjoy a one-year warranty and 24-hour customer service. Note: Due to variations in face shape, there may be slight air leakage around the nose or chin, ensuring safety without being a product defect. There may be a slight odor after long-distance transport, simply clean with water or ventilate for a few days to eliminate it.