This replacement O-Ring is for the plastic carboy lids on both the 6 and 7 gallon Fermonster Pet Carboy.
Disclaimer - These carboys are made of glass and should be handled with extreme care. We have been able to use both hot and cold liquids in them, but they are not impervious to thermal shock and can shatter when exposed to large, sudden changes in temperature. Use caution.
Note - The breather cap is now clear plastic, not black plastic