Allow me to clarify for you. The Nabu comes with two sizes of extensions. You order one, you order both sizes. You just attach the necessary link. When you buy, it won't give you an option. It will just come with both links.
Each size has 2 different clasps for sizes. The small-medium has 2 clasps, and the medium-large has 2 different ones. There are technically 4 sizes.
