material The respiratory lung expander is made of quality silicone. It is nontoxic, odorless, harmless and environmentally friendly, so you can use it with confidence. Easy to use Put on the respiratory lung expander and breathe slowly and deeply through your mouth. Hold your breath for a few seconds, then slowly exhale through your mouth until fully exhaled. Repeat 1015 times to complete a series. Perform 2 to 4 sets per day. Improve endurance Regular use trains the respiratory muscles of the chest, expands anaerobic capacity, and improves oxygen absorption, helping to increase your exercise limits. Adjustable resistance The trainer features a rotary valve design that allows multiresistance adjustment during breathing. It provides effective lung training, improves respiratory function, and promotes deeper, more efficient breathing. Use scenarios Athletes and active individuals can incorporate sessions into training to boost endurance and oxygen uptake during workouts. Daily users can perform breathing training to improve overall lung capacity and respiratory efficiency. Warmup or cooldown routines can include the device to promote deeper breathing and better breath control.