S.C. Code Ann. § 12-33-430

For the purpose of this article "a standard case of alcoholic liquors" is a package or case containing not more than three gallons and not less than two and four-tenths gallons and any package or case containing more than three gallons or less than two and four-tenths gallons shall be taxed proportionately, based on the total tax per standard case as levied in this article for each three gallons. Provided, that for alcoholic liquors offered for sale in metric size containers "a standard case of alcoholic liquors" is a package or case containing not more than twelve liters and not less than nine liters and any package or case containing more than twelve liters or less than nine liters shall be taxed proportionately, based on the total tax per standard case as levied in this article for each twelve liters.