Wine corks come in a few different sizes - the smaller the size, the smaller the cork. For example, #7 corks are smaller than #8 corks. Use #7 corks only for .187 ml size bottles. #8 & #9 corks can be used in all standard wine bottles (.375, .750 and 1.5 ml). The #8 corks are a bit smaller in diameter and length than #9's. Use #8 corks for short term storage. If storing your wine for longer than 2 yrs, use #9 corks to assure a good seal.
Corks should be rinsed off with water and a bit of sanitizer (One Step, metabisulphite, etc.) Corks can be soaked for a few minutes in hot water to make them a bit easier to insert.