The system of 4 resistance levels makes this mask ideal for all users, for training enthusiasts to world class elite athletes.The system of 4 resistance levels between 3000 and 18,000 feet makes this mask ideal for all users, for training enthusiasts to world class elite athletes. High quality materials make this mask light and comfortable to use, which does not slip off during training. High quality materials make this mask light and comfortable to use, which does not slip off during training. Increases maximum aerobic capacity (VO2). Increases and conditions lung capacity by creating pulmonary resistance.Fits most adults (120 lbs - 230 lbs/54 - 104 kg).
