Midwest suggests using only #8 corks with the plastic plunger corker. Larger corks are just too difficult to load into the corker, and even more difficult to force into the bottle. The reason that the plastic plunger corker is the one we include in our starter kit is that most winemakers eventually upgrade to a floor corker (#8253, 8254, 8256, 8258).
The plunger corker allows us to offer a wine-making equipment kit at a reasonable price. Two upgrades, the Double Lever Corker (#8201) and the Gilda Single Lever Corker (#8202) are available for only a few dollars more, respectively.