✅ SCIENTIFIC - Only Sportsmask designed for use with the scientific technique to perform altitude training at sea level [Oxygen Advantage] ✅ EXPERT DESIGNED - Designed by internationally renown breathing expert Patrick McKeown ✅ INCREASED PERFORMANCE - Delayed onset of fatigue and lactic acid, improved aerobic performance, strengthen core and breathing muscles, reduced breathlessness during exercise ✅ ADAPTABLE - Secure grip head straps to ensure mask stays in place + Varied resistance settings for your training needs ✅ PATENTED - SportsMask Patent Number US9914017