If you're talking about the ones for the fuel alleys........you didn't hear this from me......because it's not a "best practice" but you can get two as fat as you can find. I had some that were too dried out to seal, so I put in a new oring behind the old one to bring it out enough to seal. So far so good, one year. If yours aren't ripped you can try soaking them in a known oring dweller, like B12 Chem. Acetone would swell them up too. All you want is enough to get them to seal, then the constant supply of gas should keep them at the right thickness.