This air option comes with a 5oz refillable cylinder and stock. This system has the most air-in-stock capacity, and is the best option for tactical paintball. For the most realistic paintball games, you want to change magazines only—not air. This system has enough air capacity for 20+ magazines. This configuration also allows you to rig a 90 degree remote line adaptor to connect a remote line to the marker while having the air tank inside the stock, giving you an instant-backup option should your internal tank run out at a crucial moment. This butt stock has 10 adjustable positions. Shot capacity: 200+ shots T68 5oz CO2 Refillable Cylinder and Butt Stock Kit This Package Includes: - 1 x 5oz CO2 Cylinder - 1 x 5oz / 3000psi Tank Butt Stock - 1 x Butt Stock Guide For International Shipping or Expedited Shipping with UPS, please contact us at Support@PremierPaintballGuns.com and we can help you.