There are several things to consider when selecting the right cork for your purpose and cellaring conditions.
TIMEEstimate the length of time you realistically expect to store your wine before drinking.
BEVELThis is the tapered edge that some of the less expensive corks have around the top and bottom of the cork. It is to allow easier insertion with hand held corkers. Take into account that the bevel does reduce the amount of surface area in contact with the neck of the bottle and it is this contact that prevents the passage of wine past the cork.
LENGTH & DIAMETERPrimarily wine corks are available in two lengths – 38mm (1.5 inches) and 44mm (1.75 inches) – and in three diameters – 21mm, 22mm, 24mm (in USA and Canada they are known as #7, #8 and #9). The length and diameter are related to the sealing ability of the cork.
Where you compare corks in the same grade, the cork with the longest length and largest diameter will give the greatest sealing capability. Floor corkers can be used on all corks, but if you are using plunge or hand corkers you may need to opt for the narrower and shorter corks.