With this device, you can connect 1L and 2L cylinders such as CO2 or mix cylinders to your existing aquarium fish CO2 tank regulator. Made of high-quality aluminum material, sturdy and durable for long service life. Compact and lightweight, easy to carry and store, convenient to use. Purpose: Connects to M10 gas cylinder to control gas flow on/off. Specification: Item type: CO2 cylinder adapter Model: M10X1 to W21.8-14 (DIN477) Note: W21.8-14 interface is only suitable for Europe, South Korea, Australia, and New Zealand Material: Aluminum Color: Black Package Contents: 1 x CO2 Cylinder Adapter Note: Light reflection and different displays may cause the color of the item in the picture to appear slightly different from the actual product. Measurement allows an error of +/- 1-3 cm.