CO2 O-Ring Washers 

If you're supplementing your indoor garden with carbon dioxide using a CO2 tank and regulator, it is recommended that you change the washers every time you change your CO2 tank. 

Maintaining the O-Ring washers give you maximum protection against CO2 leakage at the tank connection points.

These plastic washers fit any standard-sized CO2 tanks.

Comes in a package of three O-Ring Washers.