CO2 regulator is the perfect accessory to attach the CO2 cylinder adapter to your existing aquarium fish tank CO2 regulator or mini beer keg controller Made of high quality copper, high hardness, not easy to damage, and long service life and lightweight, easy to carry and store, easy to use. Not recommended for carbonation, but ideal for dispensing Professional manufacturing, stable performance, high reliability TR21-4 Internal Thread to W21.8-14 External Thread Cylinder Adapter Color: gold + black Material: copper Package Contents: 1 x Soda Bottle Adapter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in a little different from the real thing. The measurement allowed error is +/- 1-3 cm.