Abstract: A flexible plastic safety cap for bottles containing pressurized liquid such as champagne or sparkling burgundy. This cap is designed for bottles having a neck open at the top and with an external downwardly facing shoulder. The cap includes an inner sealing portion which goes into the opening of the neck and an outer locking portion which includes a flexible, resilient tubular section that surrounds the neck. The tubular section includes two or more internal rib portions which engage the neck shoulder to lock the cap to the bottle neck. The tubular section may also include an integral pull tab portion for readily releasing and removing the cap from the bottle.