These plastic champagne style corks are ideal, when used in conjunction with the champagne style metal cages, for sealing bottles of sparkling wine or for resealing opened sparkling wine bottles for short term storage. These are in packs of 12.
If you are attempting to make sparkling wine (in suitable, recycled "Sparkling Wine" bottles - normal wine bottles are not strong enough and will explode under pressure), you will need to bottle the wine as soon as primary fermentation has finished, but before adding any form of stabiliser that would usually be used to kill off the yeast.
The "live wine" needs to be added to the bottle and "primed" with 1/2teaspoon of sugar. The bottle is then turned upside down and the yeast is allowed to drain into the hollow cork.
Once it is clear, the neck of the bottle is placed in iced, salted water and left to cause a "plug" of ice to form in the neck of the bottle. The cork can now be removed and replaced by a fresh, clean cork, leaving the CO2 in solution and keeping the wine fizzy. (Well, that's the theory.....)