Tank O-rings should be a 015. Most cocker bolt o-rings should be a 112 but some were thinner and like an 015. If you're getting a lot of drag, you could try 111 o-rings on the bolt if it used the thicker O-rings or a 014 (also work on tanks) if it used the thinner ones.
Note: While I would love to take credit for his work, I am not associated with Mad Customs!
Originally Posted by senghing27
You can contact BigMatt-MadCustoms in his MCB forum