Precision Needle Valve -
This Needle Valve is most suitable for Aquarium use. With a 56 turns / inch and 3° tapered, it can provide down to 10 bubbles of CO2 / minute consistently (at 0 pressure). Fits most CO2 Regulator Kits on the market. Inlet - Male Threaded NPT 1/8" (measures 1/4" OD physically) / Outlet - Hose Barb 1/8" (or 4/6 mm ID/OD tubing). New 'Inline version' has 1/8" barb outlet and inlet. For use with airline  or co2 proof tubing.