How do I upload multiple sizes?

Is there an option for uploading multiple sizes of the same model? Or do I have to make a different item for each? I make earrings and they come in a variety of sizes. I would like to have them available in multiple sizes but contained inside of one item, maybe with a drop down menu. This kind of thing will be a make it or break it sort of deal. Where I might not bother if I have to upload all 10 or so and set up each individually.

Thanks if any one can help.