Abstract: An oxygen lance for steelmaking is provided with a top adapter assembly of generally T-shaped configuration including a central tubular barrel and a transverse top plate which both contain the O'rings required to assure complete adequate sealing between the oxygen gas and the cooling medium utilized in the furnace.The O'rings are placed on the outside circumference of the central barrel and are held in place in grooves therein so that they cannot be accidentally displaced during oxygen blowing or during assembly and disassembly of the lance. Access to the O'rings is simplified and assured while maintaining complete sealing integrity of the T-shaped top plate and complete sealing reliability during operation. The T-shaped top plate carries the sealing O'rings in grooves provided in the tubular vertical barrel and in a transverse plate thus providing means whereby interchange of the bottom assembly in the lance combination is quickly achieved in the field or factory.