A cryosurgical instrument disclosed in U.S. Pat. No. 4,269,390 employing a standard, double walled, evacuated, metal vacuum bottle or dewar, has a collar metallurgically bonded to the top of the dewar near the mouth thereof to provide machine threads for releasably engaging a cap having internal threads which comprises the delivery and control portion of the instrument. The cap has a valve mounted thereon which controls the flow of nitrogen from a feed tube in the dewar to a nozzle mounted on a delivery tube. The valve is opened by a valve operating lever. The cryosurgical instrument of said patent has been in service around the world, with minor modifications, since 1976. Sometimes, the main valve becomes loose and leakage results.