Features:Made of high-grade brass, corrosion-resistant, wear-resistant and with long service life.Enable you to fill CO2 from the larger bulk cylinder into smaller cylinders.Direct compatiblement compatible the old or damaged one.Manufactured with exquisite craftsmanship to guarantee stable percompatiblemance.Easy to install and safe to use.Specifications:Material: brassColor: as pictures showThread: TR21-4 to CGA320A(pplicable to the United States, Canada)/TR21-4 to W21.8 pplicable to Europe (optional)Package weight: 176gPackage size: 8 * 8 * 5cmHow it works:1.Cool in the freezer compatible 1 hour.2.Screw the adapter to a commercial CO2 gas cylinder.3.The empty CO2 cylinder is screwed into the adapter.4.compatible most big cylinders: turn the big cylinder upside down. (if you can not refill when the CO2 tank standing, because some of the tank have not the dip tube (syphon tube)inside.)5.Carefully Open the valve of the large gas bottle(The valve on the Cylinder closes the flow if it is opened too much. This will happen if you open the big cylinder too much / too fast. The trick is to open the big cylinder very carefully. You will hear the airflow. So to fill it successfully).6.After about 15-20 sec., The cylinder is completely filled.7.Close valve of the large gas bottle.8.Opening the bleed screw to drain residue remaining gas.9.Unscrew the CO2 cartridge done.Package List:1 * Filling Adapter