Feinwerkbau (FWB) air cylinder, you need a specific Feinwerkbau filling adapter that screws into your pressurized air tank or compressor hose.
Feinwerkbau uses a proprietary cylinder thread, so you cannot fill the cylinder directly from standard scuba tanks without this adapter.
Types of Adapters FWB to DIN 200/300: The most common adapter features the Feinwerkbau cylinder thread on one end and a standard DIN 300/200 bar thread on the other (designed for scuba tanks or 3,500 high-pressure compressors).
FWB to Foster Quick-Disconnect: Allows you to connect your FWB cylinder to a modern PCP charging hose