Tested and approved, Spare Air is a totally self-contained 3000 psi (207 bars) refillable backup breathable gas system. Now available in two models. The 300-N is a 3.0 cu. ft. (85 liter) of nitrox gas, refillable backup breathable gas system that's small and easy to use. It was designed to get you to the surface in the event of an emergency; yet, it is small enough to not even know you are wearing it! The 300-N provides approximately 57 surface breaths. The new 600-N 6.0 cu. ft. (170L) provides a larger gas capacity suitable for deeper dive requirements. Spare Air is easy to use and maintain, just put it in your mouth and breathe. Kits include easy refill adapters so you can fill directly off your own scuba cylinder. Spare Air for Nitrox is suitable for nitrox gas up to 40% out of the box. So, give yourself that extra edge of safety with Spare Air. The 300-N cylinder measures (L x Dia.) 13.4 x 2.25" (34 x 5.71cm) and weighs 2.2 lbs. (985g) when full. The cylinders water volume is 27 cubic inches (0.44L). The 600-N cylinder measures (L x Dia.) 13.5 x 3.25" (34x 8.3cm) and weighs 3.7 lbs. (1.7kg) when full. The cylinder water volume is 54 cubic inches (.88L). The 600-N provides approximately 114 surface breaths.