Specifications: The cylinder refill adapter is made of premium metal material to make sure it is durable and sturdy to use. With the features of TR21.4 thread, the adapter is easy to install and use. There is bleed hole on side of the adaptor for reducing the risk of rest air/CO2. This product provides with different standard of the adapter for you to choose, which is able to meet your different needs. Item Name: Cylinder Refill Adapter Material: Aluminum Alloy Thread: TR21.4 Style(Optional): Style A: Adapter with One Bleed Hole Style B: Adapter with Two Bleed Holes Style C: Adapter with One Bleed Hole+Male Connector Style D: Adapter with Two Bleed Holes+Male Connector+1500psi Gauge Features: Durable, Portable, Easy to Use Adapter Size: 10cm x 5cm x 5cm/3.93" x 1.96" x 1.96" (Approx.) Notes: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Style A Package Includes: 1 x Cylinder Refill Adapter with One Bleed Hole Style B Package Includes: 1 x Cylinder Refill Adapter with Two Bleed Holes Style C Package Includes: 1 x Cylinder Refill Adapter with One Bleed Hole 1 x Male Connector Style D Package Includes: 1 x Cylinder Refill Adapter with Two Bleed Holes 1 x Male Connector 1 x 1500psi Gauge