Having a redundant air supply in an emergency can make either a self rescue or that of your buddy safer and easier then sharing air or octopus breathing. XS Scuba's Pony Bag utilizes your BCD Cylinder Straps and connects your Redundant Air Supply to your Primary Diving Cylinder. The Pony Bag is equipped with a Bottom Strap that adds stability for a more secure feel when moving through the water. Your Pony Bottle won't go anywhere with the Dual Velcro Straps that keep the Pony Bottle Secure. When you exit the water you won't experience and additional dead weight due to the Self-Draining Mesh Bottom. Pony Bottle Bags are available in three sizes depending on your Pony Bottles Capacity. Choose from a 6, 13 and 19 cubic foot (170, 368 and 538 liter) models and bags are designed to accommodate Worthington, Catalina or Luxfer Pony Bottles. Bags are manufactured with Durable Nylon for long life. BG406 - Fits 6 cu. ft. cylinder BG413 - Fits 13 cu. ft. cylinder BG419 - Fits 19 cu. ft. cylinder