The NV-55-18 Micro-Fine™ Needle Valve.
Featuring 1/8 NPT ports and the same rock solid internals as the original NV-55, the NV-55-18 mounts easily directly to a regulator or other assembly.
Popular in aquaculture, hydroponics, and other CO2 injection applications. Flow rates are identical to the original NV-55. Buna-N seals - compatible with CO2