This is the Zeagle 20 cu ft Pony Bottle System with Razor Regulator Features: 20 cu ft Aluminum Cylinder Zeagle RaZor Regulator/Valve Combination with a 36 hose Envoy 2nd stage Many different mounting options Multiple purposes Integrated tank valve Fill adapter included Can be filled by using a standard tank with fill adapter If you are doing deeper dives, or dives in an extended overhead environment, then you need that added time that a larger cylinder will give. The Zeagle 20 cu ft Pony Bottle System is a Totally Redundant Breathing System that includes a 20 cu ft Aluminum Cylinder, a Zeagle RaZor Regulator/Valve Combination with a 36" hose and a balanced Envoy 2nd stage. There are many different ways to mount the 20 cu ft Pony Bottle System Redundant System to your BC. Using our Heavy Duty Pony Bottle Bands the 20 cu ft pony bottle can be mounted next to the main cylinder tucked out of the way while the Envoy 2nd stage can be clipped to a D-ring in the front of the BC. For mounting the pony bottle in front of the diver you can use our Tank Pouch to clip it to your BC&';s D-rings. Nearly any mounting can be achieved with these accessories. The RaZor regulator acts as an integrated tank valve and piston 1st stage. Replacing the standard tank valve allows the pony bottle to become smaller and lighter while the piston style 1st stage paired with the balanced Envoy 2nd stage is a rugged and reliable regulator for pony bottle use. Filling the cylinder is done with the included Fill Adapter at any dive shop&';s filling station. Weight: roughly 12 lbs (empty) "