High-quality Material: Made of high-quality aluminum alloy, Sturdy, stable and reliable, can be used for a long time and not easy to damage. Function: internal thread TR21-4 to external thread W21.8-14 cylinder adapter, cylinder regulator Easy To Use: small and light, easy to carry and store. You can convert the soda machine filling adapter by yourself. Not recommended for carbonation, but suitable for dosing. Wide Range Of Applications: can be used for aquarium CO2 cylinder soda water cylinder adapter regulating valve We're Here for YouThank you for your trust. If you have any questions, please message us through Amazon- we'll be glad to assist.