Bought a pack of 6. I only needed one but as I had more I decided to replace the seals on 3 other gas bottles at the same time. Within 1 month all 4 seals started to leak. Upon examination, each lump became soft and "soft" (best I can describe). It looks like the material the gasket was made of was softened by gasoline. Now I have 4 leaking gas bottles instead of 1. I regret breaking 3 old seals. Do not buy!